1 - Not technically. You can move the device to anywhere you can get a wifi signal (even taking it on vacations cross country and, in a lot of cases, overseas). though, this is a pain in the ass, so getting more than one would prevent the need to disconnect and reconnect it every time you went to a different room.

The older Roku 2 (and newer Roku 1) supports HDMI and RCA. Both these devices are somewhat laggy on Youtube, since Google got stupid and forced HTML5 on everyone (read as highly CPU intensive). The Roku 3 was created originally to combat this. It's still watchable on Roku 2's, but it's something to be aware of.

2 - Wifi is default, but they also come with ethernet jacks for direct connections.

3 - No, not really. But, honestly, their system is both fast and cake to navigate, so even with 50+ stations it's not wieldy. Though once you cross 100, you may find it so. You'll probably find like me, you really only end up watching half a dozen anyways. You can organize the order and placement of channels to your liking, putting more commonly watched channels at the top.

- They also have an Amazon channel for it, so if you ever decided to do Amazon Prime, I see no benefit to going with the Fire over it, And you can always rent movies from the multitude of channels available at will.