Can I make a career as a corporate lawyer after completing 3 year LLB from Rajasthan University?

You can get a specialisation in Corporate law or rather, you can do your LLM in that. Simply doing LLB won't help these days because corporate firms give more weight-age to graduates from National Law Universities these days rather than traditional universities.

For the corporate law, you need to have either BBA LLB or MBA LLB. So, you can pursue MBA along with LLB.