Diploma

For this course you must have 10th certificate as well as 12th certificate also.

If you are talking about Dr D.Y Patil, it is the best private college in Mumbai.
Doing B.E/ B.Tech from Dr D.Y Patil is a good choice.
Good luck.

Hi,
Diploma would be 1-year course and Bachelors would be 3 years' course.

Yes some of evening college there.

If you want to study abroad after Diploma then you don't have much scope. Yes, there are a few universities around the globe that will help you to do your higher studies after Diploma but not many for sure.
But if you meant for job then there are so many chances around the world where a Diploma engineer can see the opportunities and go for them.

Correspondence electrical engineering course will provide distance learners with the knowledge of electrical engineering skills and technical skills required to design, evaluate and develop electrical systems.
If you're fascinated with the working of electrical devices and have a deep interest in physics and maths, then you already possess some of the key electrical engineering skills and an electrical engineering degree is perhaps for you.

Jobs:
The employment scope is very limited. All good companies prefer engineering graduates (or atleast someone with 15 years of education). Only in core fields (civil and mechanical) they have good pay and also respect. Other streams are not up to these major stream for providing mass opportunity to students
So, please complete your graduation otherwise you will face the stigma of Diploma holder.

Polytechnic is not a degree. It's a diploma. You can do degree after diploma.

Hi Kshitij,
You can do BE or B.Tech after polytechnic. Then, after your degree, you can do ME, M.Tech or MBA.