Any account new or old can never be banned for fake followers. Can you imagine how easy it would be for the competitors to not let any new account survive by just sending fakes? You are combining two things here. Ofcourse the trust score will be low and if he tries follow/unfollow strategy he might get more blocks. Besides even if any profiles are buying fake likes i have seen their actual ER goes down as these likes come from datacentre proxies and Instagram does punish for it. But they can never ban an account on solely that reason.
It was ~ 1 year in a half ago. Yes it did have a lot of drop haha
Aged account with posts and followers. It was ~ 1 year in a half. Roughly ~35% stayed, but the majority dropped off.