It's reasonably standard. The last money in gets to be the first money out. It solves the problem of a startup taking money from a new investor and then immediately disbursing it to the old investors (or other similar shenanigans).
The existing shareholders have to vote to approve the new round. They wouldn't do so unless they thought it overall worthwhile.
The existing shareholders have to vote to approve the new round. They wouldn't do so unless they thought it overall worthwhile.