you want the ball glitch? simple. i'm going to tell you what to do on the v4..but there is a different way on the v3 that i don't know. :/
buy LOTS OF FOOD from the shop..then delete as much as you can. eventually, your default foods (such as scones, sushi, etc.) start disappearing. Keep buying and deleting until you scroll through your foods and find balls and items. there's your ball glitch! you can eat them but they don't go away, and when you keep scrolling through you find interesting glitch items that can either freeze your tamagotchi, or give them super high skill points!
this next part is from my experience, they don't kill them, but i have gotten a glitch where my young memetchi appeared dead, but it was part of the glitch. when i reset and download she came back but my points were gone, and shop items didn't have real prices..they had a glitched value.
many things can happen when you do the ball glitch but it can cause other glitches that you may not like, such as my seemingly dead young memetchi ^_^ . if you want to reverse this glitch, you have to do a complete reset, unless you can ignore all the balls and items you can never buy again.