Answer 1

a free 3d modeling/animation program you could use (for characters/weapons/environment) is blender, there's plenty of vids on YouTube for tutorials

Answer 2

Try Unreal Engine 4. Unreal Engine is a very robust game making system that uses C++ to make games, or blueprints that allow you to make a game without having to know any languages. Check it out.
https://www.unrealengine.com/what-is-unreal-engine-4

Answer 3

A suggestion could be C# and then check out Unity. A ton of other engines, frameworks and languages can however be used for developing games.

Answer 4

Java. JavaFX. JS. ....
NOTHING ELSE