Actually there is no version number but the file's latest change was 2017-01-19. I don't remember what was changed, but it's three years better/newer than previous upload.
Balloon nightmares. Batman and Robin take turns. Just watch it.
I considered switching to red weapon for Batman, since Red 5 has a very strong charged attack (240 per attack, same damage as charged Red 7) but the Joker spends too much time at the edges of the screen, so it isn't worth it. Too many projectiles will miss and the charge is gone pretty soon after the fight starts anyway. Went with Green 6 instead.
Curiously it's better to charge up Batman with the lower level weapon Green 6 instead of Robin with Green 7 for the boss.
2161 frames ahead of test movie, which means around 521 frames were saved in this level. The test movie ends here, so no more comparisons are possible after this.
Switching to the green weapon turns out to have been the right choice. It loses a few frames on the first boss appearance but more than makes up for it in the other two appearances.