Can Reveillark bring itself back from the graveyard?
Reveillark cannot target a Reveillark card in the graveyard, including itself. While it is in the graveyard, it has its printed characteristics, including 4 power. There are currently no cards that can change the power or toughness of a creature card in a graveyard. So, once it is in the graveyard, it is not a legal target of its own ability, even if it had power 2 or less while on the battlefield.

However, there is a way to get a very similar effect. If you have a Clone, for example, copying a Reveillark, and the Clone dies, it will have power 0 while in the graveyard, and it will be a legal target for the triggered ability. So it can bring itself back, and copy the Reveillark again, effectively achieving the same outcome that you are looking for.