Config and Set command in CLI is not working while enabled VDOM

My machine is 60Dwifi with firmware 5.0.13

Having encountered a problem during the setup procedures about the site to site IPSEC connection with my VPC AWS after enabling VDOM. After setting up the Phase 1, phase 2 and it's tunnels, the Downloaded VPN Configuration from AWS asks me to config with following commands under VDOM root,

However, it give me this,

FWF60D4615023625 # config system interface

6735: Unknown action 3

Command fail. Return code -1

BTW, is "Set BTU xxxx" is not working on 60D?

Really need to settle these problems.... thank you so much!