My take on Resolution is to just pick one and use the Scale Inner to make it fill the screen. I use Anchor behavior to keep my HUD onscreen no matter what aspect ratio the user's device has. Lots of android devices seem to use 1920x1080, which is the same aspect ratio as 800x600. I personally develop in 800x600 because smaller assets means faster load time.
You can do lots of things without an actual phone, but for final testing, you should definitely borrow one from a friend or pick up a $50 outdated piece of junk on craigslist. The old phone will be a more strenuous testing environment than a newer, faster one
Lots of android devices have no keyboard. I think the giving focus to a Textbox summons an onscreen touch keyboard, but I haven't fooled around with it.