is one have to first clear the JEE mains and then give the examination of a AIEESE or he/she can give it before mains

Dear student,
Jee mains and aieese are two different examination. The eligibility criteria of aieese says that the candidate must have passed or must be appearing 10+2 (Class- XII) or its equivalent with 60 % marks in all subject. So there is no condition regarding jee mains for aisee. You can see the same on the official website of aieese:
https://www.aieesesecondary.co.in/eligibility%20criteria#:~:text=The%20candidate%20must%20have%20passed,(Secondary)%20%2D%202021%20provisionally. (https://www.aieesesecondary.co.in/eligibility%20criteria#:~:text=The%20candidate%20must%20have%20passed,(Secondary)%20-%202021%20provisionally.)
Jee mains is to be cracked to be eligible for jee advanced.