Diploma

They can assist you with job notifications but 100% placement is not at all offered by Frankfinn or any academy for that matter.

A degree course is always better and recognised than a Diploma course. So opt for the degree course.

You most certainly can.

Sir, if you are looking for fees in Acharya Institute of Technology via COMEDK, then the tuition fees is 7.0 - 8.0 lakhs and hostel accommodation is 4.8 lakhs(approx.) for 4 years.

Hello Ma'am,
Yes, of course, you are eligible for the above course. Just go for it and have a bright future.
Good Luck

These are the university guidelines:
Full-time eligibility:
The admission to UG programmes is purely based on the marks obtained in the Higher Secondary Examinations.
Part-time Eligibility: Completion of Diploma with a minimum number of 2 gap years.
Admission Process Admission forms, applicable only to ACT, MIT and CEG are released online on the website in the month of October. Rank lists based upon the Diploma score are hence released and counselling is conducted based upon the ranking.
To put it simply, you can't get admission immediately after your Diploma.

There are a limited number of seats and it depends upon the total allowed intake of the college too. Roughly around 20.

No, you can do a certificate course only. Read "IGNOU COMMON PROSPECTUS" carefully (Simultaneous Registration clause).
All the best.

Yes, you can get admission in petroleum engineering. Apply for it in any college. No problem will occur.