10 Best Places to Visit in Russia - Travel Video
if you're on WiFi you can use pretty much whatever you want app-wise, regardless of your plan. Calls and voicemail retreival over WiFi is free on projectfi for sure, but I have my doubts it would be free on TMobile (I've never used it).
Just to clarify: project FI iş Google's own mobile network that only works with select few Android phones, so it might not be the way to go with your clear iPhone preferençe.
Bottom line - get a local sim from one of the big three (beeline, MTS, megafon).
It should cost anywhere between 5 and 10 dollars, with that same amount preloaded.
Should last you through a couple of weeks. Make sure your iphone is unlocked, though.