Regarding bank not realising my property document

On which conditions, did the bank sanction the vehicle loan?

Vehicle loan is sanctioned based on my business transaction 

One spare key has given to the bank for mortgage for the vehicle 

I think without any hypothecation the bank will not grant any loan.

 Bank can exercise right of lien and refuse to return original documents until vehicle loan is repaid 

However both the loan accounts are separate and independent even though the borrower may be the same

You can file a complaint before the consumer grievances redressal commission within your jurisdiction for deficiencey ins ervice as well as for unfair trade practice. 

Unfair trade practices are any business practices that are deceptive, unethical, or fraudulent, and that can cause injury to consumers.

In principle, education loan is santioned against the future earning capacity of the student. As such, it was unnecessary for you to furnish security for sanction of education loan to your son unless there were execeptional circmstances.