Daily Puzzle no-1 -- Medium Level

why is this puzzle so long?

btw there was a mate with b7#

I know this puzzle😂

changed no mate on b7 anymore

no... at move 15 you can play b7 mate

just change the puzzle and make the last move 15. b7#

i know but black can play better and not get mated on b7

i failed this puzzle!

19. Kc6 would lead to a faster checkmate, 19... Kb8 20. b7 Ka7 21. Kc7 Ka6 22. b8=Q but in the puzzle king to a6 allows black king to escape however kc6 keeps black on the back rank after b8=Q