Dear student,

If you get yourself registered in class 12th, and then drops and again give class 12th exam next year, and give jee advanced in that year, then I must say that will be your last attempt in jee advanced.

Because in jee advanced you are allowed to give only two attempts. If you got yourself registered, then you got registered yourself with that session. And your class 12th passing year will also be in that session. And this record will be maintained wether you have dropped or not.

And thus, you can give only a single and last attempt in jee advanced. Because your first attempt was over in your dropped session.
And if you think that after dropping and next year you will appear for jee advanced and you will be given two chances, then you are wrong. You will be given only single attempt in jee advanced.

Also check out the following link to know more about jee advanced :-
https://engineering.careers360.com/exams/jee-advanced