A charger that is close to the right amps will work, but may get very warm during use. If you are worried about it breaking or the battery dying or starting a fire, get an exact match.
For the most part, laptop makers have slightly different cutouts for their CD drives, although the internal connectors are mostly the same. Some have regular rectangular holes for the CD drives, some have some intendations, they are not all interchangable. The answer is "it depends".
If there is a boot option for a USB Hard Drive, it will boot off a flash drive. Should be USB-HD probably in the BIOS.