RDS 2012 R2 Collections & UPD Quota

We have a Windows 2012 R2 based RDS Session Host environment deployed.

There are six RDSH server which are configured into two Collection of 3 RDSH each.

In each Collection the UPD Disk Quota is set to different size such as 10 Gb and 30 GB.

Access to the collection is set by choosing users group membership in AD.

My query is as follows

1. If a user is a member of RDSH Collection-One with UPD quota of 10GB and we wish to move him to another Collection-Two with UPD disk Quota of 30GB just because he has fully utilized to 10GB quota, can it be simply done by changing his group membership to allow him access to Collection-Two
2. If we change the users group membership to grant him access to Collection-Two, will he still retain his old UPD VHDX file and will the UPD grow dynamically to a new size of 30GB?

Thanks