That does sound like quite a variation for new(?) batteries. If NiMh behave the same way as NiCd the it is ok to discharge them to 0V (In fact large capacity single cell aviation cells used to be supplied with a shorting clip fitted)..What kills them is where you have multiple cells in series and one cell gets forced reverse polarity by the other cells as the whole pack gets discharged.
The important thing (I assume you're going to be using them in series stacks) is that their capacities match well. If not, the above situation can occur. They will at least need constant current charging at C/10 rate for longer than 14 hours to ensure that they all become fully charged and the cell voltages equalize.
Edit: To answer your middle question - always assume that new batteries are discharged and require a full charge before use. There are some special 'low self-discharge' cells that are retail packed as 'pre-charged' now, but that's not what you have bought.