Railways

There are no special colleges for Indian railways.

It's not necessary. It totally depends on the recruiters whether they take you or not.

Government exams and the IT certifications you mentioned are different things. Understand the fact that government exams are aptitude based. You will have to prepare Maths, English and reasoning.
If you are preparing for government exams and in your spare time you think of doing these certifications

It is must for any government. Job or government colleges.

Result is declared on 4th march. You can check it.

During a job, you cannot pursue the regular B.Tech course. AMIE may the good option for you. You can also seek about the colleges (AICTE approved) offering B.Tech part time course, but NOC will be required from Railways for pursuing such B.Tech courses.

Yes, distance education is valid for government jobs. For government jobs, selection process is same. So, no partiality is possible. Where only written exams are conducted, you can be rest assured that you are treated like any other regular degree candidates.