It differs for different tissues. For example a sperm may survive for 2-3 days, an ovum survives for about 24 hours. Some cells face biological death many hours after the person has died. That's how the concept of cadaveric organ transplant comes in.

Can help you with the next course of action and treatment plan. Would like to discuss in details and provide apt solution. Kindly consult.

Cells divide and die when in living body. Like skin cells. But not all type cells do such. Nerve cells don't die normally and don't regenerate if they die due to any disease.  Different cells has their different role and depending on their position and role they die and regenerate.  Cells usually grow by dividing itself into two. During our growth inside mother's womb a lot of cells die physiologically to create organs and give them the proper shape and size.