How do I make a mobile game auto save and load?

Simple question, maybe not simple answer.

I want to set up an autosave system for my mobile game in the event the user accidentally exits before they mean to or at the very least when they exit it saves their current data without needing to click a "save" button.

Upon returning to the game from a cold start I would also like the game to check for saved data and allow the user to "continue" if they wish.

Is this easily done? I have a hard time exporting and testing on my Android device so I'm trying to cut down the work time be asking here instead.

Thank you!

You could use browser commands such as when the back or home button is pressed use the save game function. However I would recommend using checkpoints instead. If the user is unaware of your auto save, some users exit after dying or messing up so they can come back later. As I'm not sure what your game is, there is the potential for it to save when they don't want it too ( I used quick save in tomb raider once as my jeep was hurtling off the edge of a cliff, and had to start the game again, I was not happy haha )