Can we create new user with same UID?? why do we need that and what is the purpose to create like that
Yes.
I have, in the past, created a temporary second user with an ID of 0. I'll do this when a vendor comes on site to install an application for example.
you can but you shouldn't. This is a bad security practice. I cannot think of any technical reason why you would need to do this.
ditto frank. If you need an additional root user, use sudo.