As for the "P.S.": Not necessarily.
Hookup Wire covers a lot of territory and can range from BARE (uninsulated) wire used in point-to-point wiring that was very common in old radios, aka, antique radios. Or it can be insulated, ranging from various types of plastics or older cloth/cambric insulations, to bare wire that has had "spaghetti" (insulating sleeving) slipped over it.
Tinned wire is the most common, but it doesn't have to be tinned. Tinned wire doesn't corrode and is therefore easier to solder, but don't limit yourself to that. Untinned wire is quite useable, and if you find a bunch of it for free, it's that much better. But for breadboarding purposes, I recommend using only tinned wire, as most solderless breadboards don't connect well to untinned wire that has a thick layer of copper oxide on the surface.
If you're using untinned wire as hookup wire, simply scrape the last 1/4" or so around the complete circumference using a knife (or sandpaper, or an emery board, etc.) to make soldering easier.
Dean