"Redbeard's Cup"

For example, at the beginning of my turn, I break through a portal and "discover" my opponent. According to the rules, I shouldn't attack. But why not? Should I run away from him or skip my turn?

It's actually unclear. What specific actions will be allowed when an opponent is discovered? I would at least list the main allowed actions, such as blocking, or clearly define the restrictions...

How many participants at a minimum advance to the playoffs? How will the pairings for the playoffs be determined: based on the position in their group, for example, when forming 2 groups? By drawing lots? Or some other way?

I disagree with the technical restart due to the map creator's fault. Such things should be excluded, as the person who generated the map reviews it in advance. A blocked dwelling can significantly affect the balance of power.

Regarding the viewing of upgrades, artifacts, and so on. If there is a time limit, it means the judge puts me in a knowingly worse situation compared to my opponent during that viewing period.

Regarding the additional game, playing a three-player game is not ideal. The game was originally designed for 2 players, and here there are 3. You can simply "gang up" on the 3rd player by default, and you don't even need to agree on it... The Berger coefficient does not take into account the rating from previous tournaments; only the victory/draw against a stronger player in the current tournament matters. By the way, why isn't a "draw" result provided for in the group stage?