These are questions best answered in your sales ticket, however wanted to answer the "Other questions" part
It very much depends on the workload we have at the time, and how easily you can get your backups done. Usually though, it can be done pretty quickly
The cloud environment scales accordingly.
If you are using the main domain with us, you would actually point to our nameservers. If you want any additions to your DNS, you simply ticket us and we can add them. This is something we do all the time.
You can. You would just drop us a message, and we can make that change at any point