If a player stays for a whole season without growing any of his stats (considering that he was a first team player), does it mean that he achieved his full potential? Or is it possible for a player to not grow in a season and grow again one or two seasons later?

He is pretty much done. I think there are very rare occasions when a player will start gaining again 1-3 seasons after he has stopped growing, but that’s, indeed, a rarity.
I have this player right now who grew 1 miserable point all last season. Now he is gained already 13 pts.

Basically, the normal standard is that when a player doesn’t gain pts in a season, then he is done!