Although avatars are new to Instagram, Facebook first rolled out 2D versions of them in 2019. Those avatars could only be used in Facebook posts and on Messenger. These new Instagram avatars can be combined with the avatar you had on Facbeook, but it's worth noting that the avatars look completely different than they did in 2019. Merging your avatars can make the process easier this time around, and allow you to use your avatar on both apps.