Thanks for the reply.
I have downloaded SDK for K64 since I didn't get for K61 as we are using the same for our project.
I still did not get the piece of logic based on Backdoor key acceptance , the Flash is unsecure.
Please find the snippet which found in Pflash from SDK
Here actually i need based on key acceptance how can we make flash unsecure and it can be ready for mass erase.
The example by itself doesn't implement the enablement of the backdoor key. The API in the example FLASH_GetSecurityState checks if the backdoor key is active in case the debugger writes the key.
To enable the key you need to check the FLASH_SecurityBypassin the fsl_ftfx_flash driver.