Can I install Apple Watch without iPhone

The Apple Watch doesn't need to be connected to the same carrier as your Apple® iPhone® when set up using Standalone mode (Set Up for a Family Member). The family member using the Apple Watch doesn't need an iPhone, but an iPhone is required for initial setup.

Can I have an Apple Watch with an Android phone?

You'll need an iPhone with the Watch app installed to activate an Apple Watch. There's no substitute for this on Android, even if your device supports Bluetooth connectivity. However, there's no reason why you can't use the two devices simultaneously.