Hi Uiri - excellent summary. To add:
Ratchet - when companies raise a down round, investors who invested at a higher valuation get issued additional shares. This effectively adjusts the price/valuation they paid. The number of shares issued depends on the type of 'ratchet' investors have. There are two main types of ratchets: 'weighted-average' and 'full-ratchet'; the latter is not company/employee friendly and is no longer common. For employees, what this means is that if there is a down round their equity will get more heavily diluted than they expect, because additional shares are issued to compensate investors who invested at a higher valuation.
IPO protections - you are correct. In late stage/pre-IPO financings, these protect investors from an IPO occurring at a lower valuation than they came in at, either through outright 'blocking rights' (preventing such an IPO from happening) or, as above, through ratchets that adjust their share price/valuation. Such IPO protection terms have increased in 2015/2016.