Hello Aspirant,

Yes, of course you can apply. See JEE-Advance has two consecutive attempts so if you are passing out from your 10+2 in 2020, then you are eligible to give JEE-Advanced at most upto 2022 and after that you will not be eligible. So if you want IIST then you can appear in JEE-Advance 2020 and your 12th result of 2020 will be considered.

For more details refer to the link given below :-

https://engineering.careers360.com/articles/jee-advanced

I hope this information helps you.

Good Luck!!