1) Wizards reprints stuff sometimes, and they seem to be aware of prices, but they can't acknowledge it officially, due to legal implications and such. They also try to keep prices somewhat stable, eg cards don't crash from 50$ to nothing they go from 50$ to 30$.
2) Spikes happen, but most often they calm down quite fast and settle at an usually slightly higher amount. Spikes usually happen when major tournaments show new tech/cards being used.
3) In new expansions, rarely. There are special "xy Mastes" set now which seem to happen yearly now (they have happened the last two years andthere will be one in 2017) that reprint some (not all) chase cards in their respective formats.
4) Old cards sometimes, yes. For very old card, there is the "reserved list", a lsit of cards they promised collectors to never reprint, so their supply is fixed. Sometimes people abuse this and do a buyout. This sometimes also happens with cards with few copies available.
5) Standard (the rotating format) cards that are only playable in standard and not nonrotating formats fall in value sharply when their rotation draws near.