How do I downgrade iOS 26 to iOS 18?

No there is no supported way you cannot revert. Also note that Android does not have any supported way to downgrade either. They can find some workarounds on the internet, but that has not always worked out well for those Android users who have tried.

Downgrading isn't officially supported by manufacturers. It isn't easy to do, it may void your warranty, and you could potentially brick your device. You should not try this unless you've got experience modifying your device's firmware.

https://www.makeuseof.com/downgrade-to-older-version-of-android/

You can certainly use Samsung if you wish. That choice is yours. Be prepared Android 16 is out and being rolled out to Samsung devices in the next 2 months. Not surprising is that their new update is featuring a new UI with transparency and blur. Android calls it Material Design 3 and Apple calls it Liquid Glass, but as usual they are quite similar.

You can't, if you installed the release version of iOS 26.

Read the information provided to you in the developers forums.

Or just wait a couple weeks for the final version to be released.

You seriously can't revert? iOS 26 is horrible, I want out of it so badly. I wish I never installed it. It's so bad I canceled my 17 Pro Max order because I don't want to be forced to use it. Is this going to force me over to a Samsung?

iOS update no 18 in my phone

I do not understand your post. Are you saying your phone has iOS 18? You want iOS 18? Which iPhone do you currently have and what is its current iOS?

How to downgrade IOS 26 i want to use IOS18

You should always buy what you want. Honestly, we don't care what you buy.