Hello ,

TNEA is not an exam it is a counseling authority like JOSSA , CSAB and JAC . But the difference is in those 3 admission is based on JEE Mains and JEE Advance but for TNEA Counseling merit list is prepared based on your 12th performance .

Yes , TNEA is necessary to get into Anna University .

Here you can check procedure of TNEA Counseling :-

https://www.google.com/amp/s/engineering.careers360.com/articles/tnea/amp

But one thing I would like to add registration form is delayed and  dates mentioned in the article is not updated it will be updated when new notifications from TNEA will be released .  So , you should check about TNEA regularly on Google to know about registration process beginning .