Two questions about how the en passant capture works

Question

I am still confused about the en passant rule. There are two possibilities regarding the capture itself that are not clear to me.

[FEN ""]
1. d4 d6 2. d5 c5 3. dxc6 b5 (3. c4 e5 4. dxc6)

Scenario 1: In main line shown above, is it possible to capture via en passant again after 3... b5 with the move 4. cxb7ep? In other words, is it possible to capture en passant twice with the same pawn?

Scenario 2: As shown in the given side variation, is it actually possible to capture the black’s pawn on a later move? Note that although the black pawn is still in the diagram, you must imagine that it isn’t.

Answer 1

En passant can only be played when the enemy pawn moves over your pawn's capture square during it's first move (moving 2 squares); so the answer to both condition 1 and 2 is no.

It is not possible for a pawn to en passant twice in a row.

My understanding is in early chess pawns could only move one space at a time, so when the 2 move rules was added they also added en passant to counterbalance the fact that you might lose a chance at capturing your opponent's pawn since he could now move over your capture square.

So, in essence, because after capturing en passant it is no longer possible for an enemy pawn to pass over your capture square, it is no longer possible for your pawn to capture en passant.

The official FIDE rules, article 1 section 3.7d states:

A pawn attacking a square crossed by an opponent’s pawn which has advanced two squares in one move from its original square may capture this opponent’s pawn as though the latter had been moved only one square. This capture is only legal on the move following this advance and is called an ‘en passant’ capture.

Answer 2

A pawn capturing en passant (the d pawn in this case), basically interrupts the passage of the adjacent (c) pawn on his third rank (c6 for you), on the way from c7 to c5. This privilege can be exercised (retroactively) only on the immediately following move.

Once the c pawn has arrived at c5 (without interruption), there is no "second change" for the d pawn to capture him.

Answer 3

If, in the original diagram, above, Black's move had been 3. ... b6, White could not have captured it with the pawn on c6. Why would you think that because Black played b5, the c6 pawn could do so? It is simply physically impossible for a given pawn to capture en passant a second time.

Answer 4

While a pawn cannot capture en passant twice under the modern law of chess, it has not always been that way. We can play fast and loose with 19th-century rulebooks, as chess was not as standardized then. This is a thought experiment regarding the old rules of chess, all for fun.

As aforementioned, the rules weren't so cut and dry in the 19th century. Many joke problems were and have been made to exploit ambiguities in official rulebooks. The most famous is the loophole that allowed promotion into any of the opponent's pieces. However, the hypothetical legality promoting into an enemy pawn, on their first rank, was and is vague. Furthermore, there is the question of how it would move.

But we can take liberties with our imagination and assume it moves like normal, including being allowed a double-step on it's first rank. For example, Lichess's chess variant Horde Chess logicallly allows this movement. If you count the transformed pawns as the "same" unit after the wrong promotion, capturing en passant twice is possible.

This takes two stages. First, White plays en passant and then advances to the 7th rank

[FEN "4k3/6p1/8/7P/8/8/5P2/4K3 b - - 0 1"] 
[startflipped ""]

1... g5 2. hxg6 null 3. g7

Now we pretend it promotes into an enemy pawn. Next, it advances forward to preform an en passant once more.

[FEN "4k1p1/8/8/8/8/8/5P2/4K3 b - - 0 1"]
[startflipped ""]

1... g7 2. null g6 3. null g5 4. null g4 5. f4 gxf3

Thus, the "same" pawn has captured en passant twice!