Answer #1:
You cannot simply go live on a discord whether you are on PC or a mobile. You 1st have to join a server or make a server after joining or making a server you can run a game come back to the discord server and click on the game it will showing in your profile then by clicking the button and prssing going live you will be live but some of the servers which are big 1st require the role to go live so you dont just go live and show something you are not supposed to see but after you get live be aware your screen will be shared everywhere you go people can see and your information can be seen by many people so be on your guard while being live hope this helps.
Answer #2:
Unfortunately, the Go Live feature is still unavailable for mobile phones. You can only go live from the Windows Desktop app. If you want to watch a stream, you can do it from both the browser and the desktop client.