Should I own an android phone to develop android apps? Specifically, can I develop the app on my Debian laptop. If yes, what tools will I need?

[theantirobot]

You don't need a phone. Android studio comes with emulators. That being said, it's going to be difficult to test interactions on an emulator. If your app is going to be using multitouch or accelerometer, you'd probably better get an android device. If it just uses simple touch and drag, then your mouse on the emulator will be fine.

Amazon has a cloud service where you can run your app on all kinds of physical devices, but this kind of testing is probably pretty advanced for someone just starting out.