How to write STM32F4 OTP Area
Is it possible to write on this OTP area at run-time under user program control


Yes. There are some details in section 3.8 (page 97) of the reference manual.

In brief, the OTP area behaves similarly to other parts of flash memory, except that it cannot be erased, and it contains a set of fine-grained lock bytes which can be used to prevent further writes.