How to retrieve deleted messages from instagram?

You cannot retrieve deleted Instagram DMs from Instagram itself — once a thread is deleted server-side there is no trash, restore or support route that brings it back — so "retrieval" only ever means finding a copy that was made before the delete. Your skepticism about monitoring tools is correct: no app, ours included, can pull a deleted Instagram message out of Meta's servers, because the message is gone from the server and the app never had it in the first place.

We build Ultimate Phone Spy, a parental-control dashboard for Android 4.0+, Windows and Mac, and we would rather lose the sale than sell you an Instagram recovery product that does not exist. What the Android build records is SMS, call logs, location and app activity on a device you administer, captured going forward (sms tracker). It does not cover iPhone, and it does not read Instagram DMs.

The copies that do survive, in the order worth trying:

1. The other participant's phone. A message deleted "for you" was never removed from their side. If you are on speaking terms, that is the whole answer, and it costs nothing.
2. Notification previews. Any device that was signed in and received the message may still hold the first lines in its notification shade or lock screen. They roll off within days, so screenshot before you research further.
3. Email alerts. If Instagram notifications ever went to an inbox, that mailbox has previews going back months — better retention than the app.
4. Download Your Information at accountscenter.instagram.com, selecting Messages in JSON. It returns the thread skeleton as Meta retains it, usually without text that was unsent.

Two honest warnings. Every paid "Instagram DM recovery" site or self-styled hacker advertising this is a scam or an account theft; Meta has no recovery API, so nobody can deliver. And reading another adult's messages without consent is unlawful in most jurisdictions — Wiretap Act, Computer Misuse Act, GDPR — regardless of who deleted what.

We covered the longer version in this thread.