1. Is it possible to keep multiple backup copies when backing up to network drive?
I realize that Windows Server Backup cannot keep multiple backup copies (unless backing up to local drive instead of remote network drive). This defeat the purpose of having a backup because when the local drive failed, the backup failed with it, isn't it?
This can still be overcome by manually rename the backup folder by adding the backup date so that it will create a new backup folder.
2. Is it possible to do a FULL backup of selected folders?
I realize that Windows Server Backup cannot do full backup if you didn't want to backup the whole server (there is also a 2TB limits if you backup the whole server). It will always perform partial backup with selected folder. Is there also a file limits if you just want to backup some shared folders?
It looks like you're needing more functionality in a backup software than Windows is able to provide in this instance. You're right, though. You'd have to rename the folder. There are workarounds for what you want to do, but it would probably require a lot of scripting that's not worth the effort. (like automatically renaming the folder)
I think you would find it easier and safer to find a 3rd party backup software like Backup Exec, CommVault, or Arcserve, etc.
You'll definitely get the functionality you're needing for now if you do.
Although Windows Server Backup is more powerful than NTBackup.exe., it still has some shortcomings.
When you cannot handle Windows Server Backup, you'd probably choose a third party software like AOMEI Backupper Server to help you.