How do I Phone/Tablet Basics

I want to make a utility that will run on either a phone or HD tablet:

1 What screen size do I start with since I want it to run on both a phone and a HD tablet? Also use 75 dpi?

2 Is there a way to scale to fit since I want it to run on different screen sizes?

3 I want to do a quick test. Is there a good tutorial on how to get your final program to load on to an Android Phone/tablet?

4 Is there a tutorial to get your program to go to the Play store for other users to buy?

1 Supported resolutions are listed on here http://v-play.net/doc/vplay-different-screen-sizes/

2 There are export options for portrait, landscape, letterbox style, fit to screen etc

3 Third-party apps required https://www.scirra.com/tutorials/809/ho ... -crosswalk

4 Developer console https://www.scirra.com/tutorials/1287/h ... oogle-play