Are there such system like this - put new members into trial member and then promote

[MonsterMMORPG]

Are there such system like this - put new members into trial member and then promote them to registered members when they reach 2 posts?

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can i change default registered member group?

[.m.]

you can put required restrictions to the registered member group ; create a new user group ;
and promote from the regular registered group to the new user group on set conditions

see group promotions guidance for more details