The earth surely isn't COMPLETELY circular, as nothing is, but what you are describing is in fact a circle. Also, it is impossible to walk on the other side of the earth. There is no gravity, what is perceived as "gravity" is just the upward acceleration of the universe. You would probably be splattered against the force between the earth and the UAU.. and that's only if you survive walking the ice wall for miles and miles before you're frozen or torn apart by violent winds in the outer lands.
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