I think you can use the users promotion system.See under Users then User Promotions on side menu.
You can set a rule so that a user automatically acquires an additional usergroup, under certain conditions.
Promotion Options ------ Promotion is active ------------- usergroup (new additional group)
Apply This Promotion While... User is a member of any of the selected user groups: Registered
User is NOT a member of any of the selected user groups: User is NOT a member of any of the selected user groups: Banned, Unregistered
The PRIMARY group is the group that they are in once the validation mechanism is successfully completed. Your promotions would then have them listed as a secondary group. There is no automated function to change the primary group from one to another - that defeats the whole purpose of the Group functions design as implemented in xenForo.
And my promotions I have
You don't.... they stay in the Registered users group...
You can have something like in the attached images. The "Member" group is the normal validated user group and does not have all permissions that a participating user has. Once the "Member" group user has posted 20 posts, the promotion kicks in and then adds them into the secondary group of "Member with over 20 posts", which has more permissions. Just remember, make your "Registered" group the most restrictive, then allow additional permissions by either promotion or manually adding the group you want as a secondary group (kind of a misnomer, as you can have them in multiple secondary groups).
Deepa the Registered group is designed to be almost featureless. It is just a switch from Unregistered to member. It can have much the same capacity in real terms as an Unregistered guest. So as a Reg. you may only see certain areas, and be unable to post, PC etc.
It's the secondary groups that give functional abilities.
Note of warning dont use the red NO on permissions at usergroup level. Anyone who has a red NO will override other usergroups they belong to on that permission ie block it.
Use the grey INHERIT permission instead.
The way I understand it I have a fundamental fork at first level between unregistered and registered.
Unreg have some red NO but when they switch to Reg. that disappears. All their secondary groups are grey or green permissions.
I have a small number of key secondary groups. These divide us into admins, moderators, and 3 other types. All members will be in one of these second level memberships. These determine the main access areas, and of course admin and mod abilities. Also level of PCs, signatures etc.
Then third level groups add additional privileges like editing articles which dont fit the main group structure.
There are also permissions attached to nodes where you can set access or abilities for that node. You do that from the node tree, look right for blue box Permissions. These permissions will not affect the groups you edit there, except for this one node.