PC recognizes keyboard pcb only as FT232R usb UART but doesnt see atmega32a behind it
There is no way you can make a FTDI chip or anything behind it look like an USB keyboard.
It is a USB UART chip and thus with FTDI drivers it will look like an USB serial port, in all operating systems, be it Windows, Mac, Linux, FreeBSD or any other OS.
So since it is a serial port, you can talk to the ATMega via the serial port. There is no way the OS or FTDI drivers can know what you have connected to the FTDI and how to communicate with it.