Logan is correct, but I'll go into more details about the first question:
You technically do not need to sync the whole blockchain, though you'll want to do it to save headaches. What you need to is sync enough to (1) get your owned outputs (or at least the ones which you will be sending), (2) get the transactions spending your outputs (or at least the ones spending the outouts you'd have tried to send otherwise), and (3) enough other outputs of matching amounts to fill up the ring signtures (to meet the minimum mixin).
If you happen to have those data, then you are able to spend your outputs just fine. This may seem to be pedantic, but it may be the way to make a lightweight client at some point.