Right click your .EXE .UPROJECT file in your project folder then switch engine versions then compile.
But first if you haven’t downloaded the latest version of Unreal Engine here is a video for your help if you want to use the Github route.
The other way is to just download the new engine version using the Epic Games Launcher.
How do you upgrade the engine version of a c++ project. I have tried various things but it doesn’t work. I find it weird that it is so difficult to do something so fundamental.
Binary modules are not compatible between engine version, you need to recompile them, there API diffrences so errors may apper and engine can’t recompile module automatically
Once you switch enigne version, regenerate VS project files (right click uproject file), open VS solution (sln file), try to compile, fix any errors that appear.
When I do that it just compiles the game in the previous version, even though I have changed the engine version and generated the project files in the uproject file.
Do not do generation with VS open and there no way sln file is not generated, and it should be. The most raw state if UE4 project have only Config, Content, Source (if it is C++) and uproject file, this is what you should contain project in repository if you had one. Try to reduce it to that state and generate VS files