In case if I wasn't clear (sometimes I forget...) You all may use any engine you want. I want you all to be comfortable with what you are working with. (It takes me like 5 months to show any interest in other engines, but I will not lie, Unreal and smile game builder along with rpg developer bakin are the great ones!) If you need help with finding a engine feel free to ask Amalgamash, Me, or Denis for help.
I don't recommend using a engine that you are not very good at.
some free to use engines:
Construct 3
Game maker studio 2 (you can also pay a small monthly fee of 4.99$ for free assets and more neat stuff!)
Unity 3d
Scratch
Godot
Adventure game studio (a personal favorite!)
Unreal Engine