https://wccftech.com/downgrade-watchos-5-beta-to-watchos-4-the-possibilities/

Can you downgrade watchOS 5 Beta to watchOS 4? It’s a question everyone is going to start asking vigorously today and we’ll answer it.

Whenever new beta software becomes available, everyone gets eager to try out what Apple has been cooking since the last one year. At times, it really doesn’t hurt to try out beta software as you have the convenience of reverting back to the publicly available version of the software by following a few steps. The only downside is that the downgrade process erases everything off your device forcing you to restore from a backup if you did take one in the first place.