welcome to the forum and UE4:).
as well as those 3 you also need a texture artist, level designer and someone to do sounds, although you can learn all that solo and it should be enough to make a game unless you want to make a big game then you would probably need more people like game designers/UI designers…ect.
well I am not a programmer or very good at explaining this type of thing but there are other people that can explain how it works but there are videos that can give you a good idea like the ones in this thread, there is also a lot of free samples/examples you can download and take apart to see how they work and the Unreal Engine youtube channel with videos showing haw to do a lot of it.
both, with UE4 you have 2 options, blueprints or C++, for C++ you need visual studio and blueprints are an in editor visual node based type of programming.
hope that helps:).