hi , can i know how to uninstall ios 14 beta from my phone

See this Apple support article—>Unenroll Your Devices from Public beta

Note that if you unenroll you will still have the latest beta on your phone. To remove it you must restore your phone to factory settings, which will reinstall the current GM release (14.1 as of today). Or you can continue using it, and when the next GM version drops you can install it over the beta.

Follow the steps in this link: link->How to uninstall iOS beta software - Apple Support