I know this topic had been discussed to death here but I don't know anyone IRL who is a flat earther. I tried to look online and I found some YouTube videos but they didn't explain a few things.

1) if the earth is flat, what's underneath the sheet that is earth?

2) if the earth is flat, does that mean it's not spinning and also rotating around the sun annually? Or do those theories still apply. Is the moon flat also and our satellite planet?

3) if the earth is flat, what reason does the entire world have to lie about it?

4) if the earth is flat, how can someone fly across the world without flying into the "ice wall" (which I guess is really just Antarctica.

Thanks in advance!