[W3t Wurx]

I am on a friends network and its a standard net-gear router/modem. I want to play a prank on him but shutting his computer down via the cmd prompt. I keep getting an access denied notice. I am assuming it is because i am not the network admin. my question is, can i make my self the network admin from my laptop without his desktops permission. i have already cracked the password for the net-gear router itself and can get the to web interface for it. Sorry if this has been asked before. I have been looking at Google and it's always kids who want to get into their schools network so nobody will reply to them. This is just a prank to pull on my friend, he's a good sport and will laugh about it.

In addition to that question I have an additional question. Is it possible to shut off other devices connected to the network, for example, could i shut down my Xbox one via cmd prompt.

Thank you in advance,
W3t Wurx.