Is it possible to get a 7-star champion to rank 3 without having done Act 8 100% or the Necropolis?

Question is in the title

Comments

YES

Maybe act 9.1 will have rank 2 to 3 gem so do act 8 exploration at least

If you spend enough money, there is always a way. These days, there's lots of offer to do it.

Hypothetically you could form the t3a from the minimal amount of pieces we get elsewhere, but it would take forever and is unlikely.