Hi,
You can change the database on which your domain name is pointing.
I have never done that with a domain name from the free 1y domain, but... 
"You'll be the owner of domain name, in case you want to use it for other purposes in the future."
 Then you must have received the access (from Gandi i think) to manage the DNS zone* of your domain name, to redirect (CNAME) visitors.

*DNS zone is already configured, but it may still point to yourexdomain.odoo.com. change it accordingly with your new DB, then

• go to odoo.com → my databases
• On the menu of your new database, you will find 'Domain names', 
• there you can unlink the existing domain name, and 
• add it (link) to the new-created database.

best,