Hi, Is there a separate eeprom available for the bluepill. If so what is the size of it? If it doesn't where can we save the non volatile data. What will be the usable memory length.
You can use built-in eeprom library which uses flash memory as virtual EEPROM or you can use EEPROM chip that communicates using any bus on STM32F103.
There is uEEPROMLib (https://github.com/Naguissa/uEEPROMLib) of I2C EEPROMs.