Yes, sure you can upgrade/downgrade anytime from your billing area.
PainlessBackup support all linux distributions. Database support is limited to MySQL and MariaDB.
No, PainlessBackup uses rsync, mysqldump and gzip which are available on all linux distributions
Login to PainlessBackup >> Click on your name on top right corner >> Billing >> Cancel Service.
No, We don't provide any refunds because we provides 15 days FREE trial.
So try it for free. If it suits your need then make payment and continue, else cancel it. If you don't renew before trial expires then service will be auto canceled.
All the backups and site information will be be deleted from PainlessBackup permanently. So make sure to download everything before cancellation.