When Bolt of Change is played (Chaos spell), if attacking damage is greater than the 2 toughness added to the development (since it is acting as a unit), is the development removed from play or is it ingnored and the development remain in play?

Basically, in terms of combat, are you treating the development as a unit and removing it from play if it takes more than 2 damage?

Be careful using "toughness" as a word for HP. It means something completely different in Warhammer than it does in many CCGs. Anyway, if you turn the development into a unit and its HP goes to zero, the unit (the development) dies and goes to the discard pile.

The better way of wording it is that it acts as a unit with 2 hp. If it ever has 2 damage tokens on it while it is still a unit, it is destroyed.