1- i can get snapshot from vm with independent-disk when is power-off
No, if a disk is in Independent Persistent mode, you cannot take a snapshot of it regardless of its power state. Try it for yourself. Set the disk to Independent Persistent and power it up. Now take a snapshot. The snapshot operation completes, but if you edit the VM's configuration you'll see it is not referencing any snapshot file. Browse the datastore to confirm. So if there's no snapshot, everything is persisted to disk immediately and is "permanent".
2- when i create an independent-non-persistent mode in my vm after restart or power-off vm it will be delete my virtual disk from OS but in article i read that when create a virtual disk with independent-non persistent after restart vm just data on disk will be delete but now after restart my virtual disk will be remove and had to add it manually from disk managment
This English is difficult to understand and I don't entirely follow you. There is no "delete my virtual disk from OS" when you restart or power cycle a VM which has Independent Non-Persistent mode set, however it will roll-back any changes made from the time you powered it on to the time you power cycled it. This is how that mode works. If you had to add the disk manually again (assuming Windows) from Disk Management, then something else was going on. It doesn't affect whether disks are unmounted or mounted from the guest's perspective.