There is only one pass on this play and it is an incomplete forward pass by A5. The direction of a pass is determined by where it was released and the first thing it touches (ground, player, or official, etc.). 2-19-2-a. The first thing this passed touched was B77. Since that was beyond where the pass was released, it's a forward pass.
The batting is legal because any player who is eligible to touch a forward pass may bat it in any direction. 2-2-3-a-3 and 9-4-1-a. Because B77 touched the pass, all become eligible to touch the pass. So it doesn't matter if A1 was ineligible earlier in the down for any reason, his touching (and thus his batting) are now legal.
What logic would be used to make this a backward pass?