There are subcategories within these rarities that make things a bit more complicated, but at the most basic level you can determine rarity at a glance by looking at the symbol to the right of the collector card number
Sure, the alternate win-con might be a little hard to pull off, but that's balanced out by giving all your Dragons indestructible
Regenerate [permanent] means: The next time [permanent] would be destroyed this turn, instead remove all damage on it, tap it, and remove it from combat if its an attacking or blocking creature. Abilities that trigger from damage being dealt will still trigger, even if the permanent regenerates
I can see a game state where a Black deck uses something like Deadly Cover-up to wipe the board, play this on the next turn to take down whatever creature your opponent used to recover, and then gets to untap and take out any remaining blockers, attack and win
It looks like the font is slightly crisper on the lower card, but its very hard to see