You don't need a Privacy Policy if you don't collect personal information from users through your Android app.
If you do collect personal information (directly or indirectly through a third party such as Google Analytics, AdMob, Mixpanel etc.), then Google Play Store requires you (and the law as well) to have a Privacy Policy in place.
Related to your questions:
Your Privacy Policy should be adapted based on what kind of personal information you collect from users. Do you collect email address, do you need camera access from users etc.?
WordPress.com open-sourced their legal agreements (Privacy Policy and Terms of Service) but keep in mind that legal agreements should be customized based on app, app functionality, and other factors.
This question is better answered by a lawyer but keep in mind that a Privacy Policy is the statement where you need to disclose what, how and why you collect personal information from users.
Depending on your country, it might be helpful to look into the following law acts on privacy of user data:
- CalOPPA in the US
- PIPEDA in Canada
- DPA in the UK
- IT Act 2000 in India
- Privacy Act in Australia