Try this ways to restrict on instagram using settings:
Tap Profile or your profile photo in the lower right to open your profile.
In the upper right corner, select More, then Settings, then Privacy.
Below Tap Restricted to limit how other people can interact with you.
Select Continue.
When you find the account you want to restrict, press Restrict next to their username. If you want to unrestrict someone, tap Unrestrict.
Tap Profile or your profile photo in the lower right to open your profile.
In the upper right corner, select More, then Settings, then Privacy.
Below Tap Restricted to limit how other people can interact with you.
Select Continue.
When you find the account you want to restrict, press Restrict next to their username. If you want to unrestrict someone, tap Unrestrict.