How can I use Custom Validation for the Input Email upon SignUp?

Currently Auth0 allows emails like {{9*9}} for email/password authentication, I do not want to allow some characters like {, } or * because of the further flow of my application.

Is there a way I can achieve this providing my custom regex?
Can I achieve this using PreUserRegistration Flow?
Ref: Pre User Registration Flow

Update on this

I am able to use my custom validation using PreUserRegistration Flow but the error highlights the Password Field instead of Email

Is there are way I can fix this?