Good question! I'll tackle of each of these separately.
You can evolve a Pokemon Prime into a Pokemon BREAK. "Prime" isn't part of the card's name and isn't even printed on the card (Raichu Prime just says Raichu, for example). In unlimited play (since this is the only place where it could occur), you can place a Pokemon BREAK on any Pokemon with the same name that it evolves from.
You can also evolve a Lv x Pokemon into a Pokemon BREAK because Lv x isn't considered part of the card's name. However, a Pokemon BREAK cannot be leveled up into a Lv x if the BREAK Evolution was played first, because "BREAK" is part of the card's name, Pokemon SP and G cannot evolve into Pokemon BREAK, Lv x or otherwise, because those symbols are considered part of the card's name.
As for retaining attacks from a Lv X, a Pokemon BREAK would be able to use whatever attacks are on the highest Evolution stage before BREAK, on the Lv X card, and the Pokemon BREAK card itself. Lv X isn't actually considered evolving by the game -- the mechanic is referred to as "leveling up." PokePowers and PokeBodies however, would not be retained because the BREAK mechanic only says that attacks, Abilities, Weakness, Resistance and Retreat Cost are retained. PokePowers and PokeBodies are considered a separate, albeit similar mechanic from Abilities, and things that affect one do not affect the other.
