I'll answer your second question first, you can use an FD Lens on an EOS Camera as a manual focus lens although obviously the camera can't control the lens aperture so you have to set that manually and then set the camera to match. This limits you to manual exposure or aperture priority. I've never done this but if you want to try you can get an adaptor from
ebay.
Your first question I assume means you'd like to reverse mount the lens? In which case it will work but you will have to do something to keep the lens aperture open. Apparently you can buy a special "macro hood" which did this (may be hard to find) or it's possible to manufacture your own from the original rear lens cap.
There are
adaptors which allow you to reverse mount the lens onto the camera or you can use an EF lens on the camera and reverse mount the FD Lens to that using an adaptor to connect the two filter rings. The latter option gives you greater magnification but you may have trouble finding a combination of lenses that give you reasonable image quality.
It could be a fun way to get started on macro photography for not
too much cost but the flexibility and quality aren't going to be close to a proper macro lens.
Good luck and if you give it a try, post some of the results here.
cheers
Dan