I imagine the problem is not all apps support older iOS versions... at least, I had this issue when I was trying to use an older iPhone as a backup day to day a

I imagine the problem is not all apps support older iOS versions... at least, I had this issue when I was trying to use an older iPhone as a backup day to day and found that half the apps I liked weren’t available at the time. Usually you’ll be lucky to support n-2 releases of iOS. For example: https://help.duo.com/s/article/1871?language=en_US https://help.duo.com/s/article/1871?language=en_US