Are teachers entitled to demand the remainder of their salaries after the institute canceled their contracts and received all its dues from the college?

Your entitlement to salaries is governed by the contract between you and the institute. If it was for one year, and the institute terminated the contract without a valid reason before its expiration, you are entitled to a full year's salary. This is because a lease (ijara) is a binding contract, and neither party has the right to terminate it without the consent of the other. So, if the lessee terminates it without the lessor's consent, they are obligated to pay the full rent. However, if the contract was for less than a year, or renewed monthly, and the institute paid you your salaries for the period you worked and did not renew the contract, then you have no claim against it. You can refer to the contracts and take the matter to court if you believe you have a right.