Hi guys, Long story short, I went to the Apple Store today because my iPhone 5 battery was swollen, causing the screen to pop out. I was offered by the Genius to get my phone replaced with a brand new iPhone 5 that runs iOS10 for the price of the battery ($79 plus tax). The caveat is, iOS10 will make the phone run slow (they won't install iOS8 on it). My current iPhone 5 has iOS8 on it (yes I never update it in fear of my phone running slow). If I went for paying for a new iPhone 5 with iOS10 installed on it, how do I downgrade it to iOS8?