e-bridge and ACBLOnline announce the following UNDO policy for tourneys:

No card-play undos under any circumstances – a card played is deemed played.

Bidding UNDOS: There are no bidding UNDOS – EXCEPT under the following circumstances ... a player makes an “obvious” misclick of a bid that is “clearly” erroneous. EG. Player meant to bid 1NT – and clicked 7NT instead. This must be patently obvious to the table, as well as, to the director. Players are requested to NOT ask for an UNDO, except in these unusual events.

Ну и что? Турнир - он и есть турнир. Хочется пошлепать картами - так в тех местах есть social rooms...