You cannot win a game of chess with just a knight because one knight alone cannot block all the king’s escape routes and checkmate him. If there are other pieces on the board that restrict the king’s movement, then a checkmate, and therefore a win, is possible with just the knight.
The Queen’s Gambit is one of the strongest possible openings for white and it probably has no equal. There could be an argument for other gambits that are stronger (such as the Blackmar-Diemer gambit) but you’re less likely to lose games with the Queen’s Gambit.
Whether you play the Sicilian defence or the Ruy Lopez comes down to which one you have prepared, who your opponent is, and what is at stake. If this is a game you must win, play the opening you’re most comfortable with. If this a game you can learn from, play anything.
You can’t use the Sicilian Defense against the Queen’s Gambit because the Sicilian Defense is a response to the move e4. That’s a king pawn move, which is not part of the Queen’s Gambit. However, there is a similar line of defense known as the Benoni Defense which you could incorporate into fending off the Queen’s Gambit.
The difference is that the Sicilian Defence is great for black while the English opening is advantageous for white. Although both strategies involve pushing the C-file pawn up two squares, the repercussions are very different for the players depending on who goes first.
If you are castling on the king’s side, you should probably bring your rook out on to the board and pay the tempo for doing so. If you are castling on the queen’s side, you should either unleash your rook immediately or move the king into a more defensible position.
Yes, you should accept the Queen’s Gambit if you are well prepared for it. Otherwise you should opot not to as it’s easy to make a mess out of accepting it.
In theory, you can’t force a win in chess if you only have a king. With just the king left, you can win the game only if your opponent resigns or your opponent runs out of time. You could also get a stalemate achieved by the 50 move rule.
Chess grandmasters know all the standard chess openings very well. However, chess grandmasters also tend to concentrate on going deep into the possibilities for a handful of openings. These openings sometimes become known as their signature moves.