qm-snapshot: specify name format and add related commands examples (#17589)

pages/linux/qm-snapshot.md

@@ -3,7 +3,7 @@
 > Create virtual machine snapshots.
 > More information: <https://pve.proxmox.com/pve-docs/qm.1.html>.
 
-- Create a snapshot of a specific virtual machine:
+- Create a snapshot of a specific virtual machine (name must start with a letter):
 
 `qm {{[sn|snapshot]}} {{vm_id}} {{snapshot_name}}`
 
@@ -14,3 +14,11 @@
 - Create a snapshot including the vmstate:
 
 `qm {{[sn|snapshot]}} {{vm_id}} {{snapshot_name}} --description {{description}} --vmstate 1`
+
+- List snapshots of a VM:
+
+`qm {{[lists|listsnapshot]}} {{100}}`
+
+- Rollback the state of a specific VM to a specified snapshot:
+
+`qm {{[ro|rollback]}} {{vm_id}} {{snap_name}}`