I'm not sure whats involved on doing a cross-platform game, but I do know that there are sufficient differences between the 3 platforms you named to...
Yes thats a possibility also but there are some drawbacks. You dont get to capture the full screen and you need to include that code on your app. So...
I would recommend to try and get community members to work as beta testers for you. I dont have one of those devices but I'm sure that some may have...