Question 3 ought to be: What does the government get out of saying that the earth is round ?
Well, I'd like to know that too. Yes, I know govts lie, and I too have plenty of examples, but the shape of the planet seems to be a lie of such magnitude and involving stuff outside the control of any government that it seems not quite what a govt would lie about. And it's a lie that doesn't seem to do the govt any good. And isn't it odd, if the Round Earth is a lie, that not a single country - not even one at war with us - has blown the whistle on that lie.
If the earth is flat then entirely new industries and sciences could be developed - and the economy would be stimulated - to explore and exploit whatever is beyond The Edge of the Flat Earth - possibly the sides of the planet have entirely different forms of plant and animal life, maybe even different forms of intelligent life.