legal – How much of a game can be protected by law?

I want to remake an old multiplayer game in commercial way and I wonder how different my game has to be not to violate some IP rights. I know so far that name and logo are registered trademarks of the company that still exists so I cannot use it. But …

How about other things such as maps or mechanics of the game? Can this be somehow protected?

If I make a new map that will NOT use a single asset from that old map (like textures, sounds or models) but will mimic the old map as much as possible, can this be problem from legal point of view?
By mimic I mean for example putting tree in excactly same position as on the old map, but the tree would be completely different model; buildings would have same plans but all the models and walls textures would be different.

Also this game has some certain amount of features (players classes, mission scenarios, types of weapons) that are being used in other games commonly so this cannot be patented.
But how about given set of these features? For example having given types of classes connected with given missions scnarios and types of weapons can be protected even though seperately they cannot be???
Is that possible?