Hi. I didnt understand well. If you have time can you explain me better ?Thank you very much. My mail mhsayli2@gmail.com

The API URL has been changed from i.instagram.com to www.instagram.com

Also getting threads is not possible without sending CSRF token.

Also there is not "x-ig-app-id" in local storage and I hard coded it.

instagram.com utilities
//
// currently I only have unsend all messages in thread implemented.
// but may add more if I need them
// (this won't work in incognito due to localStorage, session, & cookie values being required)
//
// To use, navigate to the thread in a web browser (I only tested with Chrome)
// and copy and paste the code into a Developer tools console
// "threadId" will need to be updated with the appropriate value
class InstagramHelper {
constructor(userId = null) {
this.userId = userId || this.getCookie("ds_user_id");
this.prevCursor = "";
this.oldestCursor = "";
}

/**

• Pause execution for n milliseconds
• This is useful for avoiding Rate Limiting errors
• @param {number} ms Number of ms to pause for
  */
  sleep(ms) {
  const end = Date.now() + ms;
  while (Date.now() < end) { continue };
  }

/**

• Get cookie value if it exists,
• Return empty string otherwise
• @param {string} name Key to lookup
• @returns {string} Value of cookie
  */
  getCookie(name) {
  if (document.cookie.length > 0) {
  let start = document.cookie.indexOf(name + "=");
  if (start != -1) {
  start = start + name.length + 1;
  let end = document.cookie.indexOf(";", start);
  if (end == -1) {
  end = document.cookie.length;
  }
  return unescape(document.cookie.substring(start, end));
  }
  }

return "";

}

/**

• Unsend all messages in the given thread
• (May need to be run a few times to completely remove everything)
• (I'm too lazy to find the optimal interval to avoid 429 errors - rate limits)
• @param {string?} threadId The thread ID
• @param {number} delay Number of ms between each delete request
• @returns {boolean} Were all messages successfully deleted
  */
  async unsendAll(threadId = undefined, delay = 3500) {
  if (threadId == null || threadId == undefined) {
  // Get the chat id automatically from the url
  var threadId = window.location.href.split('/')[5];
  console.warn("Starting deleting from thread Id : " + threadId);
  }

const threadLink = "https://www.instagram.com/direct/t/" + threadId;
// Array of message ids
const itemIds = [];
// Array of delete message ids
const deletedItemIds = [];
// Messages hash (keyed by id)
const messages = {};

while (this.prevCursor != "MINCURSOR") {
  let getMessageAPIUrl = "https://i.instagram.com/api/v1/direct_v2/threads/" + threadId + "/";
  if (this.oldestCursor != undefined && this.oldestCursor != null && this.oldestCursor.length > 0) {
      getMessageAPIUrl = getMessageAPIUrl + "?cursor=" + this.oldestCursor + "";
  }

  const requestOptions = {
    "credentials": "include",
    "headers": {
        "accept": "*/*",
        "accept-encoding": "gzip, deflate, br",
        "accept-language": "en-GB,en-US;q=0.9,en;q=0.8",
        "sec-fetch-dest": "empty",
        "sec-fetch-mode": "cors",
        "sec-fetch-site": "same-site",
        "x-ig-app-id": localStorage.getItem("instagramWebFBAppId"),
        "x-ig-www-claim": sessionStorage.getItem("www-claim-v2"),
        "x-requested-with": "XMLHttpRequest",
        "user-agent": "Mozilla/5.0 (iPhone; CPU iPhone OS 12_3_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Mobile/15E148 Instagram 105.0.0.11.118 (iPhone11,8; iOS 12_3_1; en_US; en-US; scale=2.00; 828x1792; 165586599)"
    },
    "referrer": threadLink,
    "referrerPolicy": "no-referrer-when-downgrade",
    "body": null,
    "method": "GET",
    "mode": "cors"
  };

  await fetch(
    getMessageAPIUrl,
    requestOptions
  )
    .then((response) => {
        if (response.status != 200) {
            throw response.status;
        }

        return response.json();
    }).then(async (data) => {
      console.log("getting messages...");
      data.thread.items.forEach(element => {
          if (element.user_id.toString() == this.userId.toString()) {
              if (!itemIds.includes(element.item_id.toString())) {
                // Keep track of just ids
                itemIds.push(element.item_id.toString());
                // Keep track of the full message in case we need it later
                messages[element.item_id.toString()] = element;
              }
          }
      });

      console.log('About to delete', itemIds)
      //#region  Deleting Messages
      for (let itemIdIndex = 0; itemIdIndex < itemIds.length; itemIdIndex++) {
          const messageItemId = itemIds[itemIdIndex];
          let alreadyDeleted = false;
          let rateLimitReached = false;
          const unsendRequestOptions = {
              "credentials": "include",
              "headers": {
                  "accept": "*/*",
                  "accept-encoding": "gzip, deflate, br",
                  "accept-language": "en-GB,en-US;q=0.9,en;q=0.8",
                  "content-type": "application/x-www-form-urlencoded",
                  "sec-fetch-dest": "empty",
                  "sec-fetch-mode": "cors",
                  "sec-fetch-site": "same-site",
                  "x-csrftoken": this.getCookie("csrftoken"),
                  "x-ig-app-id": localStorage.getItem("instagramWebFBAppId"),
                  "x-ig-www-claim": sessionStorage.getItem("www-claim-v2"),
                  "x-requested-with": "XMLHttpRequest",
                  "user-agent": "Mozilla/5.0 (iPhone; CPU iPhone OS 12_3_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Mobile/15E148 Instagram 105.0.0.11.118 (iPhone11,8; iOS 12_3_1; en_US; en-US; scale=2.00; 828x1792; 165586599)"
              },
              "referrer": threadLink,
              "referrerPolicy": "no-referrer-when-downgrade",
              "body": null,
              "method": "POST",
              "mode": "cors"
          };

          alreadyDeleted = deletedItemIds.includes(messageItemId);
          if (!alreadyDeleted) {
            await fetch(
              "https://i.instagram.com/api/v1/direct_v2/threads/" + threadId + "/items/" + messageItemId + "/delete/",
              unsendRequestOptions
            ).then((response) => {
              const message = messages[messageItemId];
              rateLimitReached = response.status === 429;
              if (response.status != 200) {
                  console.error(`Message skipped... ${messageItemId}: ${message.text}`);
                  console.log(response);
              } else {
                  console.info(`Deleting... ${messageItemId}: ${message.text}`);
                  deletedItemIds.push(messageItemId);
              }

              if (rateLimitReached) {
                // Add item to end of list so it can be retried later
                itemIds.push(messageItemId);
              }
            }).catch((error) => {
                console.error(error);
            });
          } else {
            console.log(`Skipping: ${messageItemId} - Already deleted`)
          }

          let sleepFor = rateLimitReached ? 6000 : (alreadyDeleted ? 0 : delay);
          this.sleep(sleepFor);
      }
      //#endregion Deleting Messages
      console.log('Done deleting batch');
      this.oldestCursor = data.thread.oldest_cursor;
      this.prevCursor = data.thread.prev_cursor;
    });
}

console.warn("All messages deleted.");
return itemIds.length === deletedItemIds.length;

}
}

// Navigate to your inbox on Instagram and go to the thread you want to delete
// The URL should be something like:
// https://www.instagram.com/direct/t/12345678901234567890
// The long list of numbers at the end is the thread id
// Because it is such a long number,
// it needs to be used as a string in this script
let threadId = "123456789012345678901234567890123456789";
let Instagram = new InstagramHelper();
Instagram.unsendAll(threadId, 1500);

// If no threadId is passed, we will try and guess it from the url
// So if this code is executed on the page containing the messages that need
// deleting it is sufficient to just use the following:
// const ig = new InstagramHelper; ig.unsendAll();