A few nuances have been clarified here
1) The blue player chooses the first Castle.
It is possible to choose the same Castle.
Starting heroes are placed randomly (by default).
2) The time limit is 8 minutes (by default).
3) Magic specialists of level 4 (Solmyr & Co.) cannot use their specialized spells at all (Coronius is an exception).
4) One subjective restart up to turn 112.
5) A summoning portal can be built in secondary dungeon castles, except when your starting Castle is also a Dungeon (this applies to "No Doublebuild").

Added 4 hours 10 minutes ago

Human translation )))
the most interesting part:
- so it turns out that you can use multiple relics, but only if they are from different combined artifacts!
and also: it is unclear - does this rule apply only to battles between opponents or also to battles with creatures on the map.

I think the question remains open... I agreed with their moderator that I would post the question about "Forbidden Artifacts" on their forum or send it to him in ICQ this evening... but the problem is in formulating the question... I just don't have time to do it right now, if anyone can do it before the evening - you are welcome.
The link to the topic is in my previous post, and the ICQ number is:
Nick: Uzza
557831389