1) is it necessary to take loan to gamble when we have no intention to pay back?
NO, it is not necessary. You will only make a trouble for yourself.
No matter what, you don't have to take loan to gamble. You should use your own money to stay away from the lender. It will be safer for you when you can not pay back the money because you gamble with your money.
2) is it necessary to commit suicide if such mistake has been made?
Suicide will not solve your problem but will left your people a new problem after your death.
You can't see how difficult your family will repay the money especially when they are hard to survive. You must think this before you decide.