Questions about factory resetting iPhone 5c.

I have had my iPhone 5c 8 gig for about six months (my first iPhone). I have almost 2 gigs of space taken up by "other" which I can't seem to clear out by any method, so I would like to take my phone back to factory condition. I have two questions:

1 -- the ONLY thing I would like to restore onto my phone after I factory reset it is are my contacts. Is there a way to restore my contacts to my phone but not restore anything else? I don't want to use a full backup, because I'm afraid that I'll put all the stuff taking up room in "other" back on my phone, too.

2 -- when I do a factory restore, will I get back the original OS that was on the phone? I do NOT want the most recent update and have not installed it.

Thanks!