Building Mac version of my game I made on windows.

I am about to begin creating my game. It is a multiplayer game.
I plan for it to be very simplistic in graphics and effects so it can run on most computers
for both macos and windows.

my question is, will I be able to build a mac version on my game on my windows PC?
Do I really have to build my game on a mac?
I have an old 2011 mac… MACOS High Sierra, 2.4 ghz intel core i5, 16 GB Ram.
I dont know if I can even run unreal engine on it and build it.

and if I do build it successfully, will I be able to play cross platform between mac and pc?

Any help would be greatly appreciated! please and thanks!

You need a mac to build the mac version.

Once you have built the game on both platforms, you should be able to have a multiplayer game between them.

You would need the same version of the engine on both, probably.