For different age categories we have different game systems.

U10 – poule system
U12 – poule system followed by elimination round
U15 and older – double elimination if over 6 participants in a weight category

U10 and U12 – no arm locks or strangling allowed
U15 – no arm locks allowed but strangling is allowed
U18 and older – arm locks and strangling allowed

Only judogi with yellow belt or higher (or equivalent in your home country) can be registered.
When in doubt, check with the tournament organisation.