why dont you try flashing both different applications separately using stm32flash. There are some tutorials on how to do this.Care must be taken that upon writing the bin at 0x08020000, the binary at 0x080000000 is not erased.you can try if jump work...

Try disabling all IRQs using __disable_irq() before performing jump.Also, in the LinkerScript (.ld) file, manually edit the line :FLASH (rx)     : ORIGIN = 0x8000000, LENGTH = 2048Kfor required values of origin and length and then rebuild.