Is there any way to copy cart backup memory to or from a PC?
The -f option can be used to copy from GBA cart->PC. There is no feature in the MB.EXE software to copy from PC->GBA cart. However, you can copy cart SRAM or Flash backup to PC or from PC to cart SRAM by using the examples in mbv2lib. Look at mbv2lib.c in the DebugLib package for an example of code to do this.