Hi

I don't understand why do you want an alternate email address or mobile no to generate otp ?..

If you have filled phase 1 application form then your email address and mobile no is still the same you will get the otp in that only.

Generate the otp, you will receive it in your mobile no and log in then you can fill the form.

You can't probably lose your registration number it must be in your admit card or email address or in your first phase application form. Pls check those once more.

Pls get back to me if you are not clear because I am not clear either about  your query.