Puzzle of the week #363

Chess Diagram: 

[Event "Puzzle #363"][Date "2019.02.24"][Result "0-1"][SetUp "1"][FEN "8/8/8/1p3B1p/p6k/P3p2P/1P1n4/4K3 b - - 0 1"]

Black's advantage in this endgame looks minimal at first glance. On top of it white has a Bishop for a Knight and the white King occupies the promotion square of the passer. Your tasks:
a) Why does black's advantage looks minimal?
b) Why does it matter white has a Bishop for a Knight?
c) Black to move and win. What tactic are you using?

Total available points for this puzzle is 20. The answers will be published next time together with puzzle #364.

Puzzle #362 solution:
Game Spiridonov – Kasparov, Skara 1980. This week's best answers are by the top players:
a) The black pieces are in best positions: Ne5 dominates the entire board, Qc5 has an absolute pin on the f2-pawn, Rb8 controls the open b-file and the King side pawns are ready for a decisive attack against the white King. Black should hope for a win

[Event "Puzzle #362"][Date "2019.02.10"][Result "0-1"][SetUp "1"][FEN "1r6/p3k3/3pp3/2q1n3/2P1Ppp1/2Q5/P3BPP1/3R2K1 b - - 0 1"]1... g3 2. Rf1 gxf2+ {This is the game line} (2... Rb1 {This is a computer move. Black sacrifices the Rook to win white's Queen at move 11. Kasparov did not see it} 3. Rxb1 Qxf2+ 4. Kh1 Qxe2 5. Qb2 Qh5+ 6. Kg1 Qh2+ 7. Kf1 f3 8. gxf3 Qh1+ 9. Ke2 Qxf3+ 10. Ke1 Nd3+ 11. Kd2 Nxb2) 3. Rxf2 Rb1+ 4. Bf1 Qe3 5. Qxe3 fxe3 6. Rc2 Nxc4 {Black resigned since it has no defence against Nc4-d2 or e3-e2}

Correct solutions:
Walter, Matthew - 20 points
Coby, Eric, Aiden - 16 points
Joey, Lucas - 15 points
Brian, Zhengyu, Glyn- 10 points
Mengbai, Blake - 8 points

Matthew - 70 points
Aiden - 62 points
Zhengyu - 60 points
Coby - 52 points
Eric - 51 points
Walter - 50 points
Joey - 45 points
Blake - 41 points
Brian - 38 points
Glyn - 32 points
Mengbai - 31 points
Lucas - 24 points
Lyvia - 20 points