Hello,
I can only answer some questions but here you go:
3.- CocoonJS supports Android 2.3 and above.
6.- The CocoonJS Launcher App provides a mock service to try in app purchases. Check out the code for our IAP demo. Anyway, I think Scirra has no support for CocoonJS IAP extension yet. Once you tested the mock implementation, the cloud compiler adds the real thing so you can try in a sandbox environment.
Regards,
Iker.