Short term

Dear, Ritika,
It's good to see that you had completed your MBA. I will recommend a few courses that you can do CFA and CRMA. You can also do big data analysis or online courses from: coursera https://www.coursera.org/courses?languages=en&query=free+courses+in+mba
It offers many courses which are very helpful for career profile. Here you will b able to select course in which you are interested. They will also provide you certificate and other benefits as per the course you choose. For further details you can visit the site as well. I hope it will be helpful for you. All the best.

Hi Rafeena,
If you are a student of regular B.Com then you cannot do any other regular degree course or Diploma as well. If you are doing B.Com correspondence then you can do any course along with B.Com with regular B.Com. You can go for some computer courses like finance and accounting courses which are short term courses.

No, it is not offering any short term Diploma course.
Refer to the college link for details: http://rizvihmct.com/

You can work on speaking skills courses. If you have interest in Analyst and Research kind of role than you can do a short course on Advanced Excel, R/Python or Big Data. If you are looking for Marketing Research kind of role than SPSS is a good tool to have hands on. Just look for the role you will be aiming during your MBA for summer/final placements. What kind of work suits you, do a bit of research on that and select a course accordingly.

In 20 days, you can only brush up the basic part in Java, learning any language completely is not possible in just 20 days, but I would recommend you to go ahead and learn as much as you can in 20 days and then sneak out few hours on a weekly basis to master Java.