You can't change tile size, and there are no user-defined types. Sorry! Luckily your third question has a more satisfying answer --multiple copies of VERGE can communicate over the internet using the netcode functions, which are documented here. It's much, much more work than a 1p game, but you can do it.

Verge's netcode is rudimentary at best, more an afterthought on an engine that up until recently was only capable of single player games. Making a multiplayer game is very much like buttering toast with a brick: it's possible, but not really the right tool for the job. If you're dead set on making something multiplayer, the easiest method is to go off and search for another games creation engine with more powerful netcode. Yes.