Hi Krileon, sorry for long time to follow up..

I have changed the setup as suggested.
Free plan
|- Plan Student member (with additional fields)
|- Plan Personal member (with additional fields)

At registration now I will see just the free plan with all related fields.

Also when I am not logged in and I will register based on the Url for "Plan Student" I will see all related fields for both plans (additional fields are required for paid plans).

But when I register for the free plan and lateron I will update to child plan how to include all required additional fields? Because these fields are not shown if I am already logged in.

Here the base requirement: I want to have basic permissions for everybody registered. Paid members should get more permissions but the plan will be activated only after confirmation by admin. And in this pendig period (could be 1 or 2 Month based on the internal process) the waiting member should have basic permissions.

If I have all plans on the same level the waiting members are not able to log in.
If I have a free plan with paid child plans I am not able to display additional required fields during upgrade for the child plans.

So my idea is now to add the waiting members to an hidden additional plan to grant basis access and remove them from this plan at time of confirmation by admin. Would this the best solution?

Sorry for long explanation but based on the long pending period I have to find a solution for this issue.
br Wolfgang