Can I use the removable storage on my digital camera to store and transfer other files (like a Flash drive)?

yes you certainly can. you can copy data to and from the card just like a usb flash device.

Probably yes. Although they are popular in use for cameras, various removable storage (SD Media and such) can be used to hold any file type (as long as the file doesn't exceed the storage capacity of your media).

Yes you can, but only if you have a card reader compatible. U can either get one as a external device, internal device, part of a floppy drive or as a USB holder.
Some examples are:

(sources)

There well worth it and very cheap (i should ask for commision ;-D). If you choosing a reader which can hold a variety of cards, check 100% that it handles the correct one.