Illegal Position Contest!

h6

There's no pawn on h6. Did you mean h5?

Yeah sorry, h5

Are those the only ones?

c7 pawn chain pawns

What does that mean? (Only one pawn is to be removed.)

FIDE competition rules.

How is this illegal???

That's what you need to show.

This is insane

Doesn't cut the mustard I'm afraid.

You reproduce the board layout with White to move after move 121B with a ply count of 12 and again after move 143B with a ply count of 56. 

Neither has a ply count of 144 and simply repeating the 34 ply sequence between the two occurrences will not land you on 144 (12+4x34=148).

Edit: Just noticed apologies to @ShouldBreezi are in order. My mental arithmetic up to its usual standard. It's a 44 ply sequence not 34 so it does work out (12+3x44=144). The sequel however still applies.

But the main problem is you're assuming that if you reach the position in the chess.com interface that means it's legal under FIDE competition rules. The chess.com interface doesn't conform with FIDE competition rules. (As a hint, because of unsolved problems in theoretical chess no current GUI conforms with FIDE rules, basic or competition.)

To illustrate the problem I've reworked the section following move 121B to repeat in 4 ply instead of 34 ply (should read 44 ply - see above edit) and repeated it 33 times so that we finish with ply count 144 (12+33x4=144).

You'll see that the chess.com interface takes the moves. 

In fact the FIDE competition rules state

9.2.2 Positions are considered the same if and only if the same player has the move, pieces of the same kind and colour occupy the same squares and the possible moves of all the pieces of both players are the same. ...

9.6 If one or both of the following occur(s) then the game is drawn:
9.6.1 the same position has appeared, as in 9.2.2 at least five times.
9.6.2 any series of at least 75 moves have been made by each player without the movement of any pawn and without any capture. If the last move resulted in checkmate, that shall take precedence.

so, under FIDE competition rules the game actually terminates on move 137B under article 9.6.1, but the chess.com GUI doesn't implement that rule.

That was just to illustrate that a game which passes as legal in the chess.com GUI is not necessarily legal under FIDE rules, so providing a proof game in the chess.com GUI is not necessarily a proof of legality. For the position I posted it's not a proof of legality.

Article 9.6.1 is not, however, the reason the position I posted is illegal under FIDE competition rules.

Proof of illegality anyone?

im gunna be pissed off if someone already did this position before me

I did a similar one, but black and white swapped places

Illegal, but legal if the white king is on c7.

I had thought #6470 is legal. As it turns out, the position is illegal when the king is on d5 - exclusively on that square.

==> bxa6 is not possible as Black's latest move as White has to promote immediately on this turn where the White pawn must occupy that very same space on b7

==> Black must have had a corner knight on a8 before it became captured, but it must have come from b6 or c7 - either way, putting the White king on d5 is illegal

==> I cannot retract the bishop move legally as well

Yep! I specifically put the white king on d5 to prevent a black knight on a8 from moving last.