It depends a lot on where you live which you unfortuneately didn't provide.
So please let me answer the best way I can step by step:
1- It starts at 68 MHZ as it's still in use in some countries notably Russia.. Only 5 countries do not use the 88-108 MHz for FM broadcasting and the radio apparently was set up for those other regions as well as where you bought it (some cheaper radios actually extend the FM band like that so the radio can be sold worldwide)
http://en.wikipedia.org/wiki/FM_broadcast_band
Depending upon where you live in the world, and the quality of the radio, sometimes you will get ghost signals of a more powerful station on those lover frequencies sometimes.. in others it will retreive the TV band in North America.
2. Probably the radio is cheap and is picking up the signal and mixing it in the radio and outputting it on another frequency..more common on cheaply built radios..... This is the Ghosts I talked about before.
3. Probably 60m,49m and 31m at night, 19 meters during the day IMO
http://en.wikipedia.org/wiki/Shortwave_bands
http://www.susi-und-strolch.de/eibi/dx/dx_e.html has frequency lists for free of what to possibly hear and when
and a website to help with some of your questions:
http://dxradio.50webs.com/