While filling the form for CUET DU LLB exam you don't get an option for LLB directly unlike LLM, in that case you get an option for a General exam that is the one which you have to select to appear for LLB  entrance.

Dear Vishal,

LL.B and LL.M are quite different in nature so as per your query I will be discussing 

LLB and LLM.  

LL.B can be of two types such as B.A.LL.B, B.B.A.LL.B, B.SC.LL.B which you can opt after passing 10+2 through other is LL.B which you can pursue after graduation with any subject under any recognised university. Entrance exams are the same as above.

Now let's come to LL.M which is a postgraduate degree in law so one who holds a graduation degree in law can opt for the entrance examination for LL.M. Such examinations are CLAT (PG) or Delhi university law entrance exam (PG) etc.

So in my view, if you don't have a law degree you will not be able to pursue LL.M 

Here are some of the best colleges after the CLAT (UG) examination you can get into,

 https://law.careers360.com/colleges/ranking/2018/top-law-colleges-in-India-accepting-clat-score?page=1 

Here is the full guide for how you can prepare for CLAT in 2019

https://law.careers360.com/articles/clat-2019

Best of luck.