if i buy an unreal engine game can I load it into unreal engine and edit it.
No you can not. You would need the project files.
No of course not. You can’t take a game that some company spent millions of hours/dollars making, and just load it up and edit it. That is like asking if you can load Microsoft Windows up in Visual Studio and edit it.
What you can do is mod games that intentionally expose pieces and parts for you to modify, and this isn’t “any unreal engine game” but only the ones that specifically do this.
It’s not an unreasonable question at all.
Bethesda’s Morrowind and Oblivion and Skyrim etc., provide superior editor programs to do just that.
All content, both official and from modders, are completely editable.
It depends on the game: Ark:Survival Evolved is an unreal based game and the dev kit is released as well. If the game developer wants the game to be modded they will give you tools to encourage it. if not then with advanced knowledge of modding you might be able to make small differences, but nowhere near as much as if you get the tools to do it.
It depends on the developer who created the game. A lot of AAA studios will not allow this but there are some who release an editor with their game. UT4 being an example.
I’m trying to edit Minecraft and play around with it, can anyone help? Maybe I can use the .minecraft file from %appdata%
you can, have a look at this: https://www.youtube.com/watch?v=ouf1zBEVeVo