Answer:
I am black within and red without; with four corners round about. What am I?
I mean goodbye for South Americans.
While you were folding a letter you got me. Usually you will do whatever it takes to avoid me but now you can't help but find me.
I am the only thing that place today before yesterday. (one word)
A large oasis in the desert. Come with cash and leave with none. What am I?
They're actually great swimmers now, but later they will become excellent hoppers.