can I do llb after. complete 12th.. and du conduct entrance exam for llb

You cannot directly pursue LLB after completing your 12th. You need to pass graduation in any discipline only after that you can opt for LLB which is a 3-year program or you can go for 5-year integrated programs like- BA LLB, BBA LLB, etc. Yes, DU conducts an entrance exam for admission into the 3-year law program and the eligibility criteria include passing an undergraduate degree with at least 50 marks. Refer to the link below for more information.

https://law.careers360.com/exams/du-llb