Hey

JEE Advanced has certain education qualification and one needs to qualify JEE Mains to be eligible for JEE Advanced. So if you just qualify Mains you will be eligible to attempt Advanced.

It depends upon which college you are seeking for admission, if you are applying for IIT, IISc, or IISER where admission is based on JEE Advanced scores, then your marks in Advanced would be considered, no matter how much you scored in Mains. And if you seek admission in NITs, DTU or other JEE Mains eligible college then you will have to score good in Mains as it would be considered only.

For further doubts, ask us.