Can a guest player have the same uniform number as a playered rostered on the team that she is guesting for?   No, the guest player must have a unique number.  Her jersey number may not match any number on the roster regardless if the player with that number is not in attendance that day. 

Does a player participating  in a US Club league have to have a USYS player pass?  Yes, she is not permitted to play on any USYS team with a US Club pass.  In order for the player to be able to use a guest pass, her team must be a member of USYS and have a USYS roster and player passes.  She may not obtain a USYS pass individually.

If we do not have a slot available on game day can a coach tell a player she is not playing because the coach is bringing a guest player?  No, the coach may not inform a player on the team roster that she is not playing because the coach wants to bring a guest player.  The only time that a coach may bring a guest player is if the roster does not exceed the maximum number of players for the day.