Sunday Special #1 : A self made study (and its backstory)

Welcome this club's first "Sunday Special"! Why is it called that? Because it's special! However, before I introduce my puzzle (from me, of course) let me share a story of how the puzzle was originated:
Back in 2010, I was still a newbie just like you guys (probably one of the weakest!), but I have read a few books and had a good tactical vision. Inspired by some of the tactical themes I saw, I decided to come up with my own "study" below:

In this position, I realized that White's plan is c4-c5-c6-c7-c8=Q. I needed to free black's pieces so I come up with the sequence 1...f6(!!!) 2.ef6 e5(!!!), freeing black's forces and blocking the white king's route, after which black will play Ke1-f1xg1xh1, winning white's two remaining pieces. However, black has countless ways of reaching his goal (according to the computer, however, my sequence is actually the best!), which makes my "study" cooked.

The reason why I decided to dig the position up again back in July 2017 is unknown, but in any case I realized the flaw and decided to change the position a bit. First, I removed the f3 pawn as well as the g1-bishop, and move the white king a bit closer to Black's camp. These small changes turned my original position from "black to move and win" to "black to move and draw". When I checked with the computer, I realized that black has to walk on a very tight path to draw! Anyways that's the backstory of this puzzle, and now, it's time for me to show the real one...and BOOM! Here it is! Just like always, please tell me how much time you took and which move is the hardest. Good luck!