it appears to be a raleigh technium mountain/all terrain bike that someone put 27" or 700c wheels on.

i'm not sure exactly what you mean by "rear fork thing" but yes, that can be used as a fixed gear. you will never be able to put a rear brake on it, however, as your wheels are the wrong size, nor will you ever be able to use the front braze-ons without switching back to 26" wheels