Can i make 2 partitions and put 2 ISOs on them so when i boot into BIOS it says something like USB(1) for first partition and USB(2) for second?
When booting into BIOS, it will only recognise the USB as 1 device, no matter how many partitions you create.
However, you can possibly create a GRUB-like OS loader on the USB. Then, when you boot onto the USB, from there you can select the OS.
The tutorial below shows how to make dual-boot USB: