Muscovy can become Russia anytime after January 1520. To be give the option it must own
Muscow (270)
and
(either Vologda (268)
or Nizhgorod (272))
and
(either Ryazan (448)
or Vladimir (271)
or Novgorod (274)
or Pskov (277)
or Tver (278)).
Also Russia must not already exist.
So if Muscovy owns Moscow, Vologda and Ryazan it can form Russia but if it owns Moscow, Ryazan and Vladimir it cannot.
-=Russian Minor (Other than Moscow) Becomes Russia=-
Russian Minors other than Moscow can become Russia after 1520. Russia cannot exist and they must own
Moscow (270) and their own capital and one of the other principalities capitals (One of
Novgorod (274), Vologda (268), Nizhgorod (272), Ryazan (448), Vladimir (271), Pskov (277) or Tver (278).)
The Nations other than Muscovy that can become Russia are Novgorod (NVG), Pskov (PSK), Ryzan (RYA), Suzdal (SUZ) and Tver (TVE).