How to fully backup and restore my site just once using SharePoint Online?
For SharePoint Online, you must use a third party tool. I hesitate to name any of them because I do not endorse any particular one, and I don't want to leave anyone out. I will name a few to help you get started though: Megalogix, AvePoint, CloudAlly, LeapBackup. Keep in mind that Microsoft also currently performs backups for your tenant and keeps them for about 14 days. If you need a restore done, you must create a service ticket with Microsoft. Using the third party software, you will be able to control when you backup, and expedite the restore.
Without using any third party software, you may leverage on Saving site as template. However, please be aware of the following limitations:
- Site collection and subsite should be backed up separately
- Limited to 50 MB
- User values will not be restored if they are not added into the sitecollection beforehand
- DateTime for the Created, Modified will not be backed up
When I performed a backup and restore previously, I used this approach. For the size retriction, I used Open with explorer to extract out all documents first. This is for me to ensure that the remainder will be less than 50MB.