Whether it can be booted from depends on the BIOS on the motherboard. Some very new ones allow it, most don't. Whether it can be seen from DOS depends on whether you can get DOS drivers for the USB CDROM. There is no single standard driver for this. You'll have to search around, the manufacturer of the drive may have one. If you use a bootable CD, the driver will have to be part of the image and in the config.sys just like a floppy boot disk.
And sword is spelled sword. 🙂