Yes, you can use a 1st generation Ryzen CPU to update a B450 BIOS.
Yes, you can use a 1st generation Ryzen CPU to update a B450 BIOS.
Maybe not. If you possess the motherboard case, locate the sticker in the lower left corner of the front panel that reads "Ryzen 3000 desktop ready," you won't need to upgrade the BIOS. Based on what I've seen, most components are compatible with Ryzen 3000 models, even the B450. If the board isn't ready (which is rare), you might be able to use it to refresh the BIOS. Remember to bring thermal paste along, as it should be changed when reinstalling your brother's CPU into his system—paste is only required for the cooler again.