what you're supposed to do in step 12 is not really a "tuck in" of the flap, but more an open sink of the flap. I've marked you the flap that you need to sink inside of the model:
yes it did help thank u very much now i know i am starting o get annoying but after i did that i tried the reverse folds and it wont go back as far as it supposed to go
Brendan
Life is too short to be serious, laugh it up.