Deworded is a characteristic-defining ability. It functions everywhere, even outside the game. For example, Ruxa, Patient Professor can return Muraganda Eldrazi from your graveyard to your hand.

Muraganda Eldrazi’s last ability will resolve before Muraganda Eldrazi does. If Muraganda Eldrazi is countered or otherwise leaves the stack in response to that triggered ability, the triggered ability will resolve is normal.

Primeval counters have their effect regardless of whether or not Muraganda Eldrazi is on the battlefield.

Playtest cards aren’t legal for play in any tournament format other than Mystery Booster Limited formats. On the other hand, we expect they will spice up a wide variety of non-tournament games (as long as everyone’s on the same page about using them!).

Playtest cards use a modified version of game symbols, such as {T} and {W}. These modified symbols should be treated as the standard symbols during play.

For many playtest cards, you’ll need to make a generous assumption that basic game rules would be updated to allow them to work. The Mystery Booster 2 Playtest Card Notes section (reproduced here in individual Gatherer rulings) provides guidance for fitting these cards into the existing rules structure.