user7894: For example, I touch my king with the left hand and my queen with the right hand at the same time. Regarding the rules, I must move a touched piece, so what would happen in this case? Could I choose which piece to move? Would I lose the game automatically when doing such an action?
Is using both hands allowed at all? (e.g.: moving one piece with both hands).
As far as I know, at least in blitz, you must use the clock and move the pieces with the same hand, so what would happen there if you use both hands when moving a piece or touching two different pieces with each hand?

user7297: From the FIDE Laws of Chess, article §4.1:

Each move must be made with one hand only.

So you are not allowed to make a move with both hands (this includes castling) and the arbiter can give you a penalty (§12.9) for this behaviour. IMHO, this should be a warning the first time you do it. In any case, because you touched the king and queen, you must make a move with either piece (§4.3):

If the player having the move touches (...) one or more of his own pieces, he must move the first piece touched that can be moved.


7894: <p>For example, I touch my king with the left hand and my queen with the right hand at the same time. Regarding the rules, I must move a touched piece, so what would happen in this case? Could I choose which piece to move? Would I lose the game automatically when doing such an action?</p>

<p>Is using both hands allowed at all? (e.g.: moving one piece with both hands).</p>

<p>As far as I know, at least in blitz, you must use the clock and move the pieces with the same hand, so what would happen there if you use both hands when moving a piece or touching two different pieces with each hand?</p>
 7297: <p>From the <a href="http://www.fide.com/component/handbook/?id=171&amp;view=article" rel="noreferrer">FIDE Laws of Chess</a>, article §4.1:</p>

<blockquote>
  <p>Each move must be made with one hand only.</p>
</blockquote>

<p>So you are not allowed to make a move with both hands (this includes castling) and the arbiter can give you a penalty (§12.9) for this behaviour. IMHO, this should be a warning the first time you do it. In any case, because you touched the king and queen, you must make a move with either piece (§4.3):</p>

<blockquote>
  <p>If the player having the move touches (...) one or more of his own pieces, he must move the first piece touched that can be moved.</p>
</blockquote>
