On my Home Screen can I show what percentage of battery is left?

There is no option to do that. You can view the % in Control Center by swiping down from the top right corner. Another option is to add the Battery widget to the home screen and it will display on the home screen in the Battery widget icon. See: Use widgets on your iPhone and iPod touch - Apple Support

You can't. To see the battery percentage remaining, you can open Control Center, by pulling down from the top right hand corner of your iPhone screen.