the posibility of spain and portugal not be eliminated

Chances are one of them will have to go. Odds are that eliminated Russia will not defeat Greece.

Greece can also qualify if it loses against Russia and Spain beats Portugal, or if it loses against Russia and Portugal beats Spain by the same score or with a bigger goal difference.

IMHO, Spain has played slightly better. It also can advance with a draw against Portugal, so...

I'm no bookie. But I'd say Greece has 90% chance, Spain 65% and Portugal 45%.

BTW, welcome to A2K.