While some universities might allow you to transfer *credits* from a B.Tech towards a B.Sc. program, this is highly dependent on the specific universities and programs involved, the overlap in coursework, and the university's transfer credit policies. It's unlikely you'd get a complete conversion; instead, you might be able to reduce the overall duration of your B.Sc. program.
To get a B.Sc., you would typically need to apply and be accepted into a B.Sc. program, possibly transferring some credits from your B.Tech if the universities allow it. The same principle applies to an NDip B.Sc. - you'd need to apply for that program.