B.Ed

Yes, I think that you can do B.Ed in distance mode after doing D.El.Ed in regular but you can not do these two courses in same session like you have to pass D.El.Ed in 2012-14 and B.Ed in 2014-2016 session.

The admission in B. Ed. is through the entrance exam conducted by the states and institutions.
Generally, the admission test is conducted in the month of May or June and the forms for the admission test are available online.
The syllabus for the entrance test is as follows:
Teaching Aptitude
General Awareness
Logical and Analytical Reasoning
General English

The eligibility criteria to seek admission in B.Ed at IGNOU is as follows: Candidate should be:
a) At least fifty percent marks either in the Bachelor's Degree and/or in the Master's Degree in Sciences/Social Sciences/Commerce/Humanity. Bachelors in Engineering or Technology with specialization in Science and Mathematics with 55% marks or any other qualification equivalent.
and
(i) Trained in-service teachers in elementary education.
or
(ii) Candidates who have completed a NCTE recognized teacher education programme through face-to-face mode.
You are eligible to seek admission in B.Ed at IGNOU.

Best colleges in Mumbai for B.Ed are:
BOMBAY TEACHERS' TRAINING COLLEGE - [BTTC], MUMBAI ; THAKUR SHYAMNARAYAN COLLEGE OF EDUCATION AND RESEARCH, MUMBAI; GANDHI SHIKSHAN BHAVAN'S SMT SURAJBA COLLEGE OF EDUCATION, MUMBAI ;K. J. SOMAIYA COMPREHENSIVE COLLEGE OF EDUCATION TRAINING AND RESEARCH - [KJSCCETR], MUMBAI

Yes, you can do B.Ed after D.Ed.

Yes, you can pursue one degree as regular and other through correspondence simultaneously.

Yes, you can pursue B.Ed after completing B.Com.