Law

See, the Distance LLB degree is not recognised by the Bar Council of India; hence, this programme is not provided by any UGC-approved university in India. Though you can check out some institutions like Mbitious Institute of Professional Studies, Atharav Distance Education, Pratham Institute of Education, Vidyasaathi, Success Path Institute of Management, etc.
These institutes will provide you with a Distance LLB degree to help you gain knowledge in legal studies, but you really can't start a Law career with it.

Since the Bar Council of India does not recognize the Distance LLB degree, IGNOU does not provide the program. But you can check out their own Law School programs, like:

• PG Diploma in Intellectual Property Rights (PGDIPR)
• PG Diploma in Criminal Justice (PGDCJ)
• PG Certificate in Patent Practice (PGCPP)
• PG Certificate in Cyber Law (PGCCL)
• Diploma in Paralegal Practice (DIPP) 
• Certificate in Consumer Protection (CCP)
• Certificate in Co-operation, Co-operative Law & Business Laws (CCLBL)
• Certificate in International Humanitarian Law (CIHL)
• Certificate in Human Rights (CHR)
• Certificate in Anti-Human Trafficking (CAHT)

Yes, a 3 year LLB Distance Education should be enough to provide the necessary legal knowledge, as the Bar Council of India does not recognize this degree, you can not go for the AIBE exam, which is a prerequisite to start practicing Law in India. Spending more than 3 years in the distance LLB program would not be a suitable choice.