for #2, we're simply in the woods. Android has support for some basic transitions, but because of the nature of the OS, you can't use them to create screen/tab transitions. So, the usual process for this is: 1. move object X pixels 2. wait Y milis 3. go back to 1 until you're done.

on #6 Android has support for a limited range of display setups, making it fairly easy to provide different UI resources for small, medium and large screens. If you want to start supporting different aspect ratios (the Droid is a good example), you have to either start detecting resolution at runtime and modify layout accordingly, or make sure you build your layout in such a way that it will adapt itself to the aspect ratio. The later is preferred, but always needs extensive testing (hopefully on real devices) because every minor OS version messes up something (1.5 has problems with PNG transparency, 1.6 with 'center' positionings, etc...).