Why can t iPhone be downgraded and can only be upgraded?

For example, after the iPhone 3G version is upgraded, you can directly restore the firmware to downgrade; If the 3GS version cannot be downgraded directly by restoring the firmware, it is recommended that you pay attention to Apple's official ** whether there is a follow-up upgrade for the system to improve the previous bugs (defects).

<> mobile phones have become the mainstream Internet terminals for rural users, and they have also become an important force for the development of the Internet in urban and rural areas. For communication operators, terminal manufacturers and other links in the industrial chain, the vast market demand and low penetration rate of smartphones in rural areas mean that there is a huge market space for smartphones to be popularized in urban and rural areas. Then here comes the problem, Android and iOS phone systems do not support downgrade and jailbreak and root.

There are many apps that are not jailbroken and rooted and are not usable. To prevent devices from being downgraded to software versions that lack the latest security updates, iOS uses a process called system software licensing. If downgrade is allowed, an attacker with physical access to the device will be able to install an earlier version of iOS and exploit a security vulnerability that has been remediated in the new version of iOS."

If you use the previous ihone mobile phone, you know that the system will be automatically upgraded, and because the old version is constantly forced to upgrade the firmware, the system will be stuck over time, and the mobile phone or iPad and other devices will be thrown away slowly.

To put it bluntly, Apple does not allow downgrades, and the fear of the device being attacked is purely an excuse!

Android devices do not allow root access and Apple does not allow jailbreak is the same, the author used ihone jailbreak and Android devices to get root access in the past, did not find anything attacked, but used it handy. The above is a little experience in my use for readers' reference.

Usually Apple devices can be downgraded freely within a week to a month after the official release of the iOS system

2. Then flash the machine through iTunes' DFU function without the help of any third-party tools.

Before upgrading and downgrading, you should be prepared for the following:

1. Pay attention to backing up data before upgrading. The iOS update will retain the user's data in the original system, but the downgrade operation will erase all the data in the phone. So before upgrading and downgrading, you should pay attention to backing up the data in your phone.

The backup and restore mechanism of iOS is that the backup data of the current version can only be restored to the current version. So if you have backed up your data under iOS 11 and think it's not easy to use and flash back to iOS 10, in this case, the backup data of iOS 11 cannot be restored to iOS 10.

Therefore, before upgrading the iOS system, you should back up the data through iTunes completely under the old system, so as not to be dissatisfied with the new system and choose to downgrade and unable to recover the original phone data. ）

2. If you need to downgrade, confirm the corresponding system firmware of the device. There are often different versions of the firmware of Apple devices, especially the early iPhone 5S and other mobile phones, which may be divided into dual Netcom and full Netcom.

3. If you want to downgrade as soon as possible. Normally, Apple will turn off the verification of the old version within a month after the release of the new version of iOS, for example, the verification of iOS 9 is turned off a full month after the launch of iOS 10. If the old system version verification is turned off, then the iPhone and iPad that have been flashed into the new system will not be able to go back to the old system.

You can use the iTunes software to reflash the backed up system to your phone on the computer that has backed up the old system to achieve the downgrade function.

Because the activation of the iOS system requires Apple's background verification, Apple's regulations are to upgrade the new version in about a few days to 1 week or at the latest 2 weeks will close the verification channel of the old system, so it becomes impossible to downgrade after this time, and the current trend is that as long as the new version is released, the old channel will be closed and downgraded within a few days after the update, and the upgrade of the iOS system will be treated carefully.

Once the iOS device is upgraded to the iOS system, it cannot be downgraded, because: 1. iOS adopts the recommended upgrade and mandatory upgrade strategy to keep the latest upgrade, and once upgraded, it is impossible to downgrade. 2. It is mandatory to maintain the latest system version to prevent information leakage to users caused by vulnerabilities in the lower version.

3. Apple has launched the ID lock since iOS7, and the prohibition of downgrade is to prevent someone from stealing the mobile phone and reusing the mobile phone through the downgrade method, so as to reduce the iPhone theft rate.

Apple is forced to upgrade the system, can not downgrade, hopefully.

Apple can also restore the previous system after upgrading the system.

In order to achieve system degradation and recovery of the Apple mobile phone system, it must be realized within the specified time, which can be used as a verification period; As long as it is within this time period, you can downgrade back to the previous version even if the device is upgraded. Once this port is down, it is not possible to revert to a lower version of the system.

Precautions for iPhone use:

1. It is best to prepare a bag when you usually use it, and put your mobile phone in it when you go out, so as to avoid the wind and sun exposure of the mobile phone in your hand, which will darken the color of the Apple mobile phone for a long time.

2. Use the Apple mobile phone to wipe it frequently, many friends do not care about this when using the Apple mobile phone, and do not wipe it after using the morning beat every day, the machine will have an old feeling after a long time, it is recommended that you wipe it with facial paper once a day, so as to protect the machine to the greatest extent.

3. Apple mobile phones are also very good for playing games, but when we use Apple mobile phones, remember not to use them for more than four hours in a row, especially to play games and watch, which will accelerate the aging of electronic components.

4. Apple's mobile phone is a relatively durable machine, and everyone's reputation is also very good, but some friends' machines are very troublesome to use, and often the machine responds slowly, in fact, this is because you ** some domestic software and Apple's mobile phone are incompatible, it is recommended that you uninstall it as well.

5. In fact, the charging of Apple mobile phones needs to be paid attention to, and it is recommended that you charge the mobile phone in time when the power is less than 30%, which can prolong the life of the mobile phone. <>

After the iPhone 3G version is upgraded, you can directly downgrade by restoring the firmware; If the 3GS version cannot be downgraded directly by restoring the firmware, it is recommended that you pay attention to Apple's official ** whether there is a follow-up upgrade for the system to improve the previous bugs (defects).