Solutions

This is position from Grandelius N. (E2562) - Grover S. (E2516).
Grandelius could play:
1. h5!, gxh5 ( 1...Nxh5 2. Rxh5+, gxh5 3. Nxe5 +- )
2. Nxb5!  It is very important with move order !
2...axb5
3. Rxh5+, Nxh5 ( 3...Kg8 4. Bh7+, Kh8 5. Rh6+-)
4. Nxe5, Ng7 ....and now comes very nice queen sacrifice
5. Qh5+, Nxh5
6. Nf7++, Kg8
7. Nh6 #
When I said that move order is very important I thought that White could also play:
1. h5!, gxh5
2. Rxh5+ ?!, Nxh5
3. Nxb5 ? With the same idea as in the right solution, but here Black has fantastic defence......
3...Rc1!! which destroys white´s coordination. Position is unclear.

In this combination was not possible to answer the question as both moves leads to advantage for White, but better move is 1...Kf8.
The position is from game Bejtovic J. (E2385) - Aagaard J. (E2506)
1...Kf8 (1...Kh8 2. Ra4! That is the point. Who would say on diagram position that this rook on a7 would take part in direct attack on black king  in just one move? White´s threats are irresistible.)
Here I missed that following continuation wins a pawn.
2. Rxd6! ( I played 2.Be4 and soon we agreed for a draw)
2...Rxd6
3 .Rxc7, Bd7
4. Be4! This is what I missed. I calculated only 4.Ba3 but after 4...g6 things were rather unclear for me. Black rook has not good squares and he will be forced to exchange it for my bishop. White would stay with a healthy pawn up.

This combination is hard to solve. Black needs to win a pawn on c4 or a5  In order to convert his advantage. To do so, he needs time to put a pressure on a5. If he plays immediate 1...Qc5 2. Nb5 and now tries to exchange on b5 with 2...Bd7 white can play 3.Ra1 and things are not clear.
That´s why Black has to play:
1...Bd7
2. Ra1 (2. Ra2, Qc5 3. Nb5, Bxb5 4. cxb5 and now 4...Qd4 with threat  Rc1+ and we can see the difference from variation in introduction. The rook is on a2! )
2...Bb5!! This is the point. Beautiful move.
3. Rd1, Qxc4! and with this temporary queen sacrifice Black wins.
This combination was from the game Swan I. (E2259) - Bejtovic J. (E2385) Glasgow 2012. I missed second move and played 2...Qc5 and went to win the game later on.

Now , it is time for three easier combinations:

In the game Debashis D. (E2446) - Yilmas M. (E2543) White did not miss to play:
1. Qh5+! in order to take away the square h5 from black king.
1...gxh5
2.g5+, Bxg5
3. hxg5 #
It is very important to have many similar mate patterns in own arsenal.
Maybe is not hard to find it during the game, but it is much harder to spot it in one´s calculation 10 moves before it actually appears on the board.

This is from the game Johansson A. (E2029) - Petersen P (E2155) .
White missed to win the game with a queen sacrifice. What was more tragic, he actually lost the game.
1. Rxf4! as indicated in comments on yesterday´s post.
1...Rxe3
2. Rxe3+, Kd8
3. Bb6+ ...and actually game does not finishes with a mate as indicated in the comment, but White has enormous material advantage.
3...Rc7
4. Rf8 and White wins....

According to some definitions of combination in chess this would not be an combination ( Someone said that combination is forced variation with a sacrifice. There is not real sacrifice here.) but as I can see this can be considered combination.
It is from the game Zude E. (E2384) - Popovic D. (E2579).
Black played:
1...Rc3 and White resigned. It can follow
2. Bxc3, dxc3+
3. Kh1 (3. Kf1, Nh2+ 4. Ke1, Qg1+ 5. Nf1, Qxf1#)
3... Nf2+
4. Rxf2, Qxf2 and there is the same material relation as before Black went for the combination. The difference is that White can not stop c pawn from being promoted.