Hogyan tudom letörölni az iPhone 5-om ró az ios 9-et?

ez csak egy pár napig lehet állítólag, miután feltetted a 9-est...

How to downgrade from iOS 9 and reinstall iOS 8 - the complete guide

Removing iOS 9 (or any other version of iOS) and downgrading to the previous version is relatively straightforward, provided you do so within a few days of launch. There's a brief window (generally just a few days) after Apple releases a new full version of iOS, during which the company continues to 'sign' (or authorise) the previous version. In those few days you can downgrade reasonably easily. Follow these steps to remove iOS 9 and go back to iOS 8:

1) Back up. Really! Back up now. During the reinstallation process, iOS will wipe all of the apps and data from your iPhone or iPad (except for the undeletable, stock apps). Make a backup of the device before you begin the following procedure.

It’s worth noting that you won’t be able to restore this backup to your iPhone as iOS 8 isn’t compatible with iOS 9 backups, and we’ll be using the archived backup we took above instead. If you haven’t archived an iOS 8.4.1 (or earlier) backup, we would advise backing up iOS 9 to iCloud to avoid overwriting the standard 8.4.1 backup on your Mac.

2) Get an .ipsw file for the previous version of iOS 8.4.1. To reinstall iOS 8, you need to acquire the iOS 8.4.1 IPSW file. If it's stored on your hard drive you can find it by following the path youruserfolder/Library/iTunes/ and then within a folder called iPad Software Updates, iPhone Software Updates or iPad Software Updates.

If you can't find the latest one on your Mac - which is fairly likely, giving the Mac's tendency to delete them periodically - then don't worry. Simply run a search for download ipsw and select and download the appropriate file for your device. There are plenty of sites to choose from.

3A) Open the .ipsw file. Assuming that Apple is still signing iOS 8.4.1 (it's likely to stop a short time after iOS 9 launches), the following steps should be fairly easy. Plug your iPhone or iPad into your Mac (or PC - the steps are essentially the same), then launch iTunes. Click on your device in the iTunes interface and select Summary. Now hold down the Alt/Option (or Shift on a PC) key, and click the Restore button. (You'll need to disable the Find My feature on the device if you've enabled it.)

Now navigate to the iOS 8.4.1 ipsw file and click Open. iTunes will now reinstall iOS 8 on your iPad or iPhone.

3B) If necessary, go into Recovery mode. If iTunes says you're already running the latest version of iOS on your device, you may need to use Recovery mode. Shut down the device, plug one end of the syncing cable into your computer and hold down the Home button on the iPhone/iPad while you connect the cable to it. When the Connect to iTunes screen appears, release the Home button.

iTunes will say that your device is now in Recovery mode. Hold down the Option key (Alt), click Restore, navigate to the iOS 8.ipsw file, and install it on your device.

8.4.1-et még aláírja, ha naprakész az ipsw.me információja.

A mentéssel nem sokra mész, valószínűleg a visszaállítás után azt fogja mondani, hogy újabb, vagy korábbi verzióról készült, és nem rakja vissza. De azért persze megpróbálhatod.

akkor még lehet rá esély.

igen, biztonsági mentésnek annyi, ha iOS 9-en már készült egy, mert visszafele nem kompatibilisek. visszaállításnál írja is, hogy iOS 9 vagy újabb kell ahhoz a mentéshez.

Itt tudod ellenőrizni. Amit le tudsz tölteni azt még aláírja az Apple

[link]