A question about R. Mika's Second enhance, namely the timing. When is handsize checked? At the time you play the enhance, or before you deal damage? Or both?

The cards in hand is checked when the ability is played. So you play the E, check do they have 4 cards in hand? If yes, then you can play a reversal before you take damage.

I'd say it checks when the ability is played, so stamp for babelfish.