I think a result or a decision is wrong

Raise it as soon as you notice, with evidence — screenshots, a replay file, or anything else that shows what happened. A dispute without evidence is very hard to act on, and the longer a round has moved on, the less can be done about it.

The organizer and the appointed referees have final authority over how a tournament is run and how the rules are read, and registering means accepting their decisions. Support can pass a dispute on and tell you what was decided; it cannot overturn a referee.

Rules can also change between events — for a legal reason, a game update or something unavoidable — and material changes are announced in advance where that is reasonably possible. The Rules tab of the tournament you entered is the version that applies to it.