Channels on our sets are only for the antenna input which you don't have. To have the set power up to other than antenna I'm always reading the product manual. But with no exact model I can't do that for you.
As to item 3 I use the usual HDMI cable.
Sorry but I have a variety of issues with my LG WebOS and I was wondering how to fix it:
1. Is there any way to set up favorite channels using a computer using my LG account rather than on TV with the remote?
2. When I switch on my TV, it is always set to live tv and since I have no antenna it makes that annoying hissing sound? How can I set it up so that it go straight to Hulu etc.?
3. I find no way to cast Youtube directly from laptop to LG TV without using screen cast?