MBA/PGDM

Yes, you can go for Ph.D after completing MBA. You must have good project work in your kitty to get admission for Ph.D from any top institute. You can publish your work on national and international journals to improve your profile.

You won’t be able to get a good college with 80 percentile in CET exam. You can get admission in an average college.
Good luck.

Yes, it will help you. The job prospects depend on your skills, which you have developed during the entire year.

Kindly refer to the link mentioned below:
https://www.shiksha.com/mba/ranking/top-mba-colleges-india-accepting-cmat/2-2-0-0-5822

It would be better for you to appear in next year's exam to get admission in a better college.

Most of the good colleges have the fee structure in the range of 10-15 lakh rupees. So, it is difficult to get into a good college with your budget.
For more details, kindly refer to the link mentioned below:
https://www.shiksha.com/colleges-accepting-cat-scores-range-70-to-80-percentile-article-1195

You have very low chances. The CMAT cut-off for MBA in GIM will be around 96-97 percentile.

Welingkar is the best option among these colleges and has a good brand value in India. PUMBA has a good ROI. Welingkar, Mumbai campus is an older one and preferred for management studies.

Kirloskar is a good B-school but not the best. IIM( all), FMS, XLRI, MDI, IIMT-Ghaziabad, SPJain and ISBM are better options than Kirloskar B-school.