3

Say I have bought an app from Google Play and already have it installed on one device.

My question is – do I have to pay again if I download this app from Google Play from another device(but same Google account)?

2

Yes, you can have your Google account on several devices and you'll be able to use all paid apps on all those devices. There is a device limit, however (around 10 I think) which is meant to prevent abuse of that.