Do you always promote a pawn to Queen?

Do you underpromote a pawn?

Sometimes but rarely underpromotion is needed to win, but ive never been in a situation when i needed to underpromote

Well, I'll give you an example

First example: Qd7 c8Q also wins, though slower.

Second example: this should really be memorized, because it's sometimes the only drawing resource in a KR vs KP endgame.

1st example: Promote to rook, black king is forced to a6, then Ra8#.

2nd example: Move your king to the other side. This will probably end up a draw.

Under-promotion is used when you need to prevent stalemate, a draw be repetition, Zugzwang, to fork, to smothered checkmate an opponent, or to be cooler. EX: If a rook can give the checkmate a queen can, checkmate with the rook

If the opponent still has some material to cause trouble I would get the queen, But if they have nothing useful left I would promote to a rook as that is all I need to checkmate and I show my scorn by under-promoting. They of course should resign when they see the pawn will be promoted. 

Under promoting doesn't show scorn, it just enables the game to carry on for longer.

The answer to the second one is promoting to knight

Sometimes you must under promote to avoid stalemate. I have also seen puzzles where under promoting to a Knight results in checkmate. Having said all of this, I don't think I've ever under promoted.

No, in a winning position with less than a minute on the clock I underpromote to a Rook to avoid any accidental stalemate.

True

An instructive example occurs in the Albin Counter Gambit. 1. d4 d5 2. c4 e5 3. dxe5 d4 4. e3 Bb4+ 5. Bd2 dxe3 6 Bxb4 exf2+ 7. Ke2 fxg8=N+.

You should not always promote a pawn to a queen. There are special occasions in which if you need to underpromote.

There are reasons you need to underpromote:

1. To Avoid Stalemate

2. To Gain an Advantage

3. To defend against a threat

4. To punish your opponent for not resigning (the 5 Knights attack)

5. Because it is check.