When you unlink your Instagram from Facebook Messenger, it typically means that the two accounts are no longer connected, and any interactions or visibility between them may be limited. However, if someone already saw your Instagram profile through Messenger while it was linked, unlinking the accounts won't remove that visibility or the fact that they saw your profile.
If you've deleted your Instagram account and then created a new one, the new account would not have any association with the previous one. Unlinking Instagram from Messenger prevents future connections and visibility, but it doesn't retroactively erase prior interactions.
In summary, unlinking your Instagram from Messenger won't remove the visibility of your old account from their Messenger, but it will stop any future interactions between the two accounts.