I asked a similar Q before and I have been doing more research on YouTube and Google. I am not quite clear yet.
Is it possible to compile a game and install it (With your serial) on your own phone for testing with only UE4?
Or do I have to have Unity to compile for Gear VR?
Thanks. Sorry to be a pest. This is all new. I got my old 3D software out and started reading again 
AFAIK UE4 has GearVR support.
I would assume you could package the game for the phone and load it onto said phone and start the game.
HTH
-Edit-
Is the Unity thing you talking about the Unity compilation option?
If so: That merges source files together to help speed up compile times.
I just was wondering if Unity was required along with UE4. I just watched a vid about this and it is not. UE4 can compile
Can I also assume you can write your C++ right inside UE4 and compile and not have to buy visual studio?
Man…This stuff is seriously complex. I knew it was a lot to take on when I started but seeing it…
Would it be reasonable to pick of a Refurb G6 to get started or is the G7 worth the money to upgrade and “Buy it once”?
If I wanted to make my game (someday LOL) just for a regular PC screen, is it pretty easy to use the same game and just change how it is compiled to port it to Gear VR later? I ask because it might be easier to learn the foundation first and add the VR at the end. I think Someone above suggested that already ;D
UE4 Uses the VC++ compiler for windows builds, But you don’t have to buy a VS liscense.
You can either use the “Express” edition(no plugins and less features) or you can use the “Community” edition(Which is free if you meet certain conditions),
But you need to read the license from the Community edition to know if you can use it for free.
Unity is a separate game engine, So you would only need it if you wanted to compare the two.
If those are computers, You would need to look at there specs and compare it to what Epic has as the minimum required specs.
BTW: The game will run better then the editor on the same hardware as the editor is more resource intensive.
You would have to take into consideration certain things about the target platforms(Controller options, How complex to make the controls, The amount of graphics detail based on platform capabilities).
I believe developing for VR requires extra considerations: Object sizing, how you handle the HMD, And probably some other stuff as well.
I think if you stay away from platform dependant libraries/functions you should be able to recompile/package the game for other platforms.
HTH