Distance/Correspondence

Yes, you can definitely go for B.Sc in Mathematics through distance education after completion of your Bachelor of engineering. Normally speaking, the eligibility for B.Sc in mathematics will be class 12th, and I am sure, you would have done your class 12th before entering into Engineering College.

You can give NET exam criteria, for NET exam the criteria is post-graduation through distance or regular.

Universities having the facility for D.Ed are:-
1)Mata Sundari College For Women, Delhi
2)Malineni Lakshmaiah Engineering College, Hyderabad.
3)Vikramaditya College, Rohtak
4)ICFAI University, Hyderabad
5)Bundelkhand University, Jhansi
Universities having the facility for D. el. Ed are:
1) Tamil Nadu Open

Here is a detailed information about top colleges in Mumbai for doing MBA in tourism. Take a look
https://www.shiksha.com/hospitality-travel/travel-tourism/colleges/colleges-Mumbai-all
I hope it will helpful to you.

For B.Ed, you have to pass graduation with 60% marks. But, B.Ed is not correspondence course, so you have to join any regular University.

According to my views and experience for Masters in statistics, you can get admission in Delhi University is most popular university in India, as well as in world. And, if you want to go in private list then there are lot of good university and many more.

Dear friend, As per my experience if you want to go for an Open University education, you must choose universities which are well known as well as reputed at world wide level or at state level. This will provide you with a good scope for future.

No, you can visit the website iul.ac.in and go through the all essential details. You can also apply through that same link. You can have all the details like fees on the website only. And if you wish and have enough time then you can also visit our university.
All the best.

Yes, you can do, but both shouldn't be regular type of courses.