Indian Institute of Technology, IIT Bombay

Working hard with patience is the only key to crack Mains and Advance. 1 year is enough time to get into the right track. Just start being calculative about the time. Before sleeping, ask yourself where you have wasted your time and how can you clear your concepts. This will surely help.

Sorry my friend but IIT does't give lateral entry. Also, the Diploma courses are of 3 years which means that you are unable to give the exam of IIT main this year.

Experience certificate from the employer is required.
The institute will conduct interview, and written test (if required).
Valid GATE score, if any would be an additional benefit.

There is no lateral entry admission in IIT Bombay, you have to clear JEE Mains and JEE Advance for getting into IIT Bombay for aerospace engineering
For course details, check out the link below:
https://www.shiksha.com/university/indian-institute-of-technology-bombay-mumbai-54212/courses?bc[]=10

Non-core companies are really not concerned about your branch, except if it is computer science. They just look for soft skills, programming, aptitude and logical reasoning abilities which you can develop in any branch.
Coming to jobs in aerospace especially for B.Tech, the scenario is not that good.