Hello.
for the complete detail about important dates for the tamilnadu Dr Br Ambedkar law University counselling date for LLB course you can go with the below link:
https://law.careers360.com/articles/tndalu-admission
If you will not find details of 4th round counselling dates then I will suggest you to go with the official website check it on the regular basis there will be update notification which will definitely give you a proper date.
Best of luck.

Hello,

If you're asking regarding LLB program of 3 years duration, then no its not possible to pursue it after diploma in engineering because eligibility criteria for it is graduation and diploma degree isn't equivalent to bachelor's degree or graduate program for that matter.

Hello,

If you are seriously willing to pursue law not just as a course of study but a career in future, consider doing law program as a full-time course, BCI has not yet approved full time Law Programs in India, most of the university offers certificate and diploma courses only in distance education.