JEE Advanced

Yes, you can practice Allen material but prepare for NCERT first. More than 30% of the JEE questions in JEE Advance are given from NCERT.

Almost all the colleges in AP take students based on EAMCET results. So, it is not possible for you to get seat in top colleges based on JEE Advanced.
I would suggest you to try NIT Warangal, IIT Hyderabad or IIIT.

As you talk of finance, you don't need to worry about that, you can manage to gain scholarship so that you can go for B.Tech because to move to ISRO you need a platform which you can get through your college. You'll get greater exposure also as doing graduation doesn't mean you go for jobs.

Well according to the 2017 notice from training band placements cell of MNIT out of 66 eligible students of electrical engineering 54 were placed with the average package of 6.58 LPA and the highest package of 16.17 LPA. This looks pretty good in terms of placements of MNIT, Allahabad. MNIT, Allahabad has always been among the top NITs of India. So it's good in terms of placements also and campus life as well.

Kindly visit this link:
https://www.google.co.in/url?sa=t&source=web&rct=j&url=https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor&ved=2ahUKEwjAu47I1_3bAhWHsY8KHZKxCSQQFjAAegQIARAB&usg=AOvVaw1N9BzFtyUCP4JU-2UQHQ0H

The counseling process of JEE Mains is through JOSAA portal. Visit its website to get yourself registered and sit in the counseling. After you've qualified JEE Mains then only you are eligible for JEE Advance examination and if you qualified advance then you are eligible for advance counseling i.e. for IITs and IISERs. You have to fill in the choices of college and branch preference very carefully if you want a college. If you don't wish to choose a college then you can 'withdraw' from the counseling round.

Hello, I am mentioning Shiksha's college predictor. Please visit it:
https://www.google.co.in/url?sa=t&source=web&rct=j&url=https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor&ved=2ahUKEwjAu47I1_3bAhWHsY8KHZKxCSQQFjAAegQIARAB&usg=AOvVaw1N9BzFtyUCP4JU-2UQHQ0H.

Hello, Please use Shiksha's predictor to find a good college:
https://www.google.co.in/url?url=https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor&rct=j&sa=U&ved=2ahUKEwi7xLvrj4DcAhVEvo8KHX1bB0QQFjAAegQIARAB&q=sissha+college+predictor&usg=AOvVaw2XP_zVyb0ocLS8jQERCtIp.

Hello,
Please use Shiksha's predictor to find a good college:
https://www.google.co.in/url?url=https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor&rct=j&sa=U&ved=2ahUKEwi7xLvrj4DcAhVEvo8KHX1bB0QQFjAAegQIARAB&q=sissha+college+predictor&usg=AOvVaw2XP_zVyb0ocLS8jQERCtIp

Hello,
Please use Shiksha's predictor to find a good college:
https://www.google.co.in/url?url=https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor&rct=j&sa=U&ved=2ahUKEwi7xLvrj4DcAhVEvo8KHX1bB0QQFjAAegQIARAB&q=sissha+college+predictor&usg=AOvVaw2XP_zVyb0ocLS8jQERCtIp