For the block that can parry attacks, I think that it would have to be "Ready'd up" before reflecting a shot; the player would have to press space on the round they reflect a bullet/beam. If this is too OP, then maybe the parry would come out one move later, this would have to create a cooldown, but it could be used when the player moves a space after activating the parry block.
Example: the player sees a bullet coming towards them and they activate their Parry block. If the bullet was 2 spaces away after they activated their parry block, then they would move up towards it and it would run into the parry. If it was 1 space away after they activated their parry block, then they could either press space again, or move into the bullet and have it run into the parry block. However, the bullet will not be reflected if it hits the parry right after the player activates it, due to the delay
This example is assuming that the parry only works if the bullet runs into the block itself, not the block in front of it.
The reflected bullet will probably have to spawn inside of the parry block to prevent bugs.