I'm not sure what you mean by age restriction.
Maybe some engines are paid and you have to sign an EULA that asks you to be at least a certain age?
If that's the case, focus on opensource engines, there are many 2D ones.
The most famous one would be Godot (3D and 2D), an alternative with graphical programming would be gdevelop
If it's a specific game, for example, an RPG, Open RPG Maker
If it's a VN, it could be Renpy. etc. etc
Now, if you know programming, instead of an engine you can use a library, and for 2D, you have SDL and SFML.