I see from your sig, Jai, that you are in the US......things are quite different in the big, wide world.
Firstly, VFR is not possible in some parts of the world.....IFR is also easier most places (less local rules to learn).
The avgas thing is simple - in many parts of the world, especially the Middle and Far East, avgas is either not available or must be ordered (often by the drum). Jet fuel is always freely available.
Filing a flight plan is not allowed, in many places, unless you have first obtained permission to overfly or land. This is usually done by country and can take up to 7 days (it also costs). You must quote the permission numbers on your flightplan form. No permission, no clearance.
As an example - to refuel in India would require 7 days to obtain clearance and still costs a couple of thousand dollars to land/handle. Before you pay for your fuel.
Your original question was to do with comms - this varies by area and altitude. Many places are only served by HF frequencies (especially over water), some have VHF at higher levels (North Atlantic, for example) and some ATC Centers have Satfone comms as well.
It's not for beginners and it's not cheap.