Can I only choose the update that I need? Can I go back to the IOS software when my iPhone was released?

No. Once updated there is no way to go back.

You can choose whether to update or not when an update is offered sure. But you cannot go back once you update.

You can only update to the most up to date iOS version your device supports at any given time. So if you had an iPhone 6 running iOS 8 for example, you would only be able to update to iOS 11 at this point. No other intermediate iOS version would be available to update to.

iOS updates cannot be reversed.

You cannot pick and choose iOS updates. You can choose to not apply the current update.

And of course you can choose which app you update, but not OS updates.

1. No.

2. No, unless it came with 11.2.2.

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