Pilot

Yes, you can do that, provided you have completed class 12th with PCM 50% marks, because this is the minimum educational requirement for pursuing CPL Training.
Your diploma shall be an additional qualification, although it shall not give you any advantage.

The salaries of pilots are similar all over the aviation market, it differs only on the basis of allowances that are paid to the pilots. Any FO can expect an initial salary of around Rs. 1.3-2.0 lacs per month. The flying allowances range between Rs. 1700-2400 per hour. Layover allowances are paid at the rate of $18-24 per day. So, for any FO who flies around 60-70 hours per month, the salary ranges between Rs. 2.0-3.0 lacs per month. For captains, the salary almost gets double i.e. Rs. 4.0-7.0 lacs per month, initially. This range includes almost all the salary packages offered by either schedules operators or non-scheduled operators.

Placement/.job depends on you. A flying school shall not provide any placement assistance. You will have to look at the vacancy notifications as and when published by the airlines and apply to them as per your eligibility. People have got placed within one month of getting their license and some others keep waiting for a longer duration due to unawareness or no vacancies being announced by airlines.

There is no such entrance exam. You can directly contact the flying school and they shall arrange for all your admission formalities.

DGCA has certain regulations which are to be followed all the time, irrespective of your flying school. The answer to your question is YES, you can do your CPL from Canada. Usually people go out of India only to complete their training faster. Canada is also one of the choices where candidates go for pursuing their CPL. You will be issued CPL by them and you will have to convert your CPL to Indian CPL. The fees will be similar to that in India. It should be around 30 Lakhs + additional cost of living.

Civil pilot or commercial pilot is the one who flies for schedule operators like Air India, Jet Airways, Indigo, etc. and for non-scheduled operators like private jets and VVIP operators and finally a pilot 'flies' the plane, it is not 'driven'.

You should be aware that the cost of CPL Training is dependent on the type of aircraft you choose to get trained on.
Cessna 152 - Rs. 7000-8000 per hour
Cessna 172 - Rs. 9000-11000 per hour
P-16 - Rs. 15000-18000 per hour
Any candidate who gets enrolled for this professional training requires to complete 200 hours of flying, in order to get his/her CPL issued.
Hence the total cost including accommodation + food goes around 25-30Lakhs.
Bombay Flying School's fee will also be lying somewhere around this figure.

No, pilot training course offers a job guarantee under Rs. 35 lacs. Only the cadet pilot programme conduct by various airlines offer job after the completion of the training. The training cost in such programmes ranges from Rs. 55-65 lacs. After doing your CPL from any usual flying school you are free to apply to any and every vacancy that is announced by airlines for the want of pilots. If you are good at your subjects and remember the procedures well you will always have a chance to get shortlisted for pilot's job.

You should confirm this from the management of the flying school. Usually, it is not a compulsion in most of the flying schools to stay in the hostel.