I apologise for not answering WRT India but you'll get an idea.
1. It depends. If they can afford to keep their instrument rating valid, they may get a job. Many don't and drift off into other careers. Exam credits lapse too.
2. Again. It depends on the market. Some people are lucky and pick up a job straight away, others are on a tagged scheme and so picked up when their employer offers a position, others, it can take years. (see point 1.)
3. The ATPL you'll get once you have a minimum of 1,500 hours and whatever else your Authority determines (e.g. 100 night, 500 hours multi crew etc) as well as pass another flight test. You should already have the ATPL exams completed.
4. How long is a piece of string? Salary is dependent on many things. Type of aircraft, position, length of service, type of operation etc. Country etc all are variables.
5. Depending on the condition, they spend some time off getting well, see their Authority for an assessment and hopefully, get their job back. For some conditions, that's it, game over.
Some conditions that are final. Diabetes requiring insulin injections, asthma requiring oral steroids to manage it, some mental conditions, significant deafness/eye sight problems, artificial heart replacement, epilepsy, some brain traumas, some migraines, paralysis etc.
In other words, watch your weight, wear a helmet and eye/hearing protection and keep happy.