IIM

Yes, you can apply for Ph.D after completing your PGDM. But it's always better to go for a full-time course if you are not an entrepreneur and have a lot of free time. You get to learn much.

No course. But, you should prepare for the CAT exam which is required to get admission in all the IIMs.

The CAT cut-off at Ahmadabad is always around 99.5 pr.

What is your CAT score?

Clear the CAT exam with higher score and Crack GDPI you will get IIM. Apart from Iims, institutes like ISB, XLRI, SP Jain, JBIMS, FMS Delhi, MDI Gurgaon offers management courses with similar exposure as IIMs.

You have to crack entrance exam to get into IIM.

Hi, You can refer the link for Iims CAT cutoff:
https://www.shiksha.com/mba/articles/how-much-cat-score-do-you-need-to-make-it-to-these-iims-blogId-13415.

Chances of getting calls from older IIMs will be low, you can get calls from newer IIMs (Kashipur, Udaipur, Raipur, Rohtak, Amritsar, Sambalpur, Bodhgaya, Trichy, Jammu). A good performance in WAT-PI will enhance your chances of converting the calls.

It depends on your CAT score. If your percentile is above 99, however, you need to be in the graduation final year without any backlog in order to be eligible for appearing in CAT.

Yes, you get weight.
The application form does ask for work experience details but it is not mandatory. However, during the final selection of candidates, work experience is given some weightage by the Iims. The exact weightage given to work experience is never revealed by the Iims but it varies from IIM to IIM.