How do I reset my watch if I hv forgotten my iCloud account and password

You can generally log-in to your iCloud account with your Apple ID and Apple ID password.

You likely use the same ID to log-in here to the Apple Community, and for Messages, FaceTime etc.

Re: "reset my Apple Watch"

Apple Support have a short video online that may be helpful:

https://www.youtube.com/watch?v=UXBcNcbTcqg