Bitsbox apps are actually web pages that can be opened in any modern web browser. As long as your tablet has a browser (like Chrome, Safari, Firefox or a newer version of IE), it can "play" apps that your kids make with Bitsbox. The operating system (iOS, Android, etc) doesn't matter at all.
Bitsbox activities will never expire or be deactivated. If you're using the "August" box, you will absolutely be able to work on activities from March, or any other time. Also, the projects in your August box will work forever, so you can stockpile them if you need to!
Yes! The real secret to Bitsbox is that the method will work on anyone—it's only the themes and graphics that make it kid-specific. As long as you aren't offended by the thought of using something with cartoon animals, you'll do just fine : )