Puzzle of the week #309

Submitted by Eugen on Tue, 02/14/2017 - 18:11
Chess Diagram
[Event "Puzzle #309"][Date "2017.02.14"][Result "1-0"][SetUp "1"][FEN "2r5/1b2kpp1/1p2n2p/pr1p4/8/P3PPKP/BP1R2P1/3RN3 w - - 0 1"]
We are near the imaginary border between middlegame and endgame with equal material and both Kings somewhat exposed. Your tasks:
a) Explain why we are near the imaginary border between middlegame and endgame
b) Who has the advantage and why?
c) White to move and obtain material advantage

Total available points for this puzzle is 25. The answers will be published next time together with puzzle #310.

Puzzle #308 solution:
Game Kasparov – Karpov, World Championship Match 1985. This time I have chosen Bradley's answers for the first 2 tasks:
The name of the opening is the nimzo-indian defence. Over the first few moves both sides have been fighting over the centre and on move 6 black trades his c-pawn for the d-pawn. This gets rid of his e-pawn. Then, in move 8, black offers another trade. White plays Rc1 in anticipation of black taking his pawn. This leaves white with an IQP. White takes advantage of the open file, and in move 16 he advances his IQP. When it is exchanged, he gets rid of his endgame weakness and controls the open files.
I think that white is winning because:
-both sides have castled
-material is even
-blacks bishop is in the corner, while white's is in the centre
-white controls the e-file and has a lot more space(blacks pieces are all within 3 rows
-blacks back rank is poorly defended(only 1 defender). This means the d8 rook is overloaded as it has to defend e8 and the d7 rook
White can take advantage of this by sacrificing his queen for the d7 rook.

[Event "Puzzle #308"][Date "2017.02.07"][Result "1-0"][SetUp "1"][FEN "3r2k1/pb1r1pp1/1pn2q1p/3B4/6Q1/P4NP1/1P3PP1/3RR1K1 w - - 1 23"]23. Qxd7 ({Yakov, Coco, Cody} 23. Re8+? Rxe8 24. Qxd7 Re7!) 23... Rxd7 24. Re8+ Kh7 25. Be4+ g6 26. Rxd7 Ba6 ({Jalen} 26... Ne5 27. Rxe5 Qxe5 28. Bxb7) 27. Bxc6 {Bradley} 27... Qxc6 ({Benjamin} 27... Kg7 28. Bd5 Bb5 29. Rxf7+ Qxf7 30. Bxf7 Bxe8 (30... Kxf7 31. Re5) 31. Bxe8) 28. Rxf7#

Correct solutions:
Bradley, Jalen - 30 points
Benjamin, Deryk - 25 points
Coco, Cody - 21 points
Yakov - 11 points

Bradley, Coco - 56 points
Jalen - 50 points
Cody - 47 points
Benjamin - 38 points
Deryk - 32 points
Uros - 22 points
Yakov - 11 points
Dheera - 7 points