How can I downgrade from iOS 26 beta to iOS 18 on my iPhone 14?

All we can do here is point you to the uninstall instructions. When installing a Beta, you are entirely on your own. Apple does not offer any support for Betas, and as such we are not allowed to offer any either in these forums beyond posting the link to the uninstall instructions.

click here ➜ How to uninstall iOS or iPadOS beta software - Apple Support

You will need to set the device to recovery mode.

How to uninstall iOS or iPadOS beta software - Apple Support

Removing the beta profile does not automatically put the current public iOS back on your device. Once you have removed the beta profile you are going to have to restore your device to install the current iOS. If you did not do a backup of your device in iOS 18.5, you will lose all of data.

Jack_018 wrote:

I removed the beta profile but it didn’t revert me back to current version of IOS and I got told from apple I have to wait till the public beta to be released to go onto that for less bugs.

If you did not back up your data before installing the beta, then yes you will not be able to downgrade without data loss. You can certainly downgrade now by installing the last stable release of iOS 18.5 and there is nothing stopping you from doing that. It does require following the steps in the link already provided.

As for the recommendation to wait for the public beta for less bugs, each beta update is going to have less bugs. That is the whole purpose of the beta program and the public beta does not mean it is going to be bug free. That just means there are more testers that are allowed and the recommendations still apply to perform a backup before installing and only use a secondary device that is not essential for daily operations.

READ the information provided to you when you joined the developers beta, including the NDA you accepted.

Since you had to be a developer in order to install iOS 26 you should already know how to downgrade. Why are you asking here? Please explain. Did you falsely claim you are a developer?

So you still haven't bothered reading the NDA...