Will a Max Hailstorm whose base move is Freeze-Dry be resisted by Water types, as the move is no longer Freeze-Dry? Or will the mechanics carry over, so the Max Hailstorm is super effective against Water types?
No, it doesn't.
Source This match. We did a battle in Nat Dex AG to find out, and it worked that Max Hailstorm wasn't super effective.
Hole this helps!
Nope, freeze dry isn't super effective on water types upon dynamaxing.