if the earth is flat explain these

if the earth is theoretically flat whats on the other side and better yet are all planets flat or is it just the earth and if its flat explain light because light on a globe would reach one side whitest the other is not reached so on a flat object (can be anything thats flat) if light were to be flashed it would touch the entire surface of the object and how would the earth look like if it was flat would it be flat on a desk or something else and also explain how you know the earth is not hollow and creatures from hell live in there theres a cap on it in the crater from the meteor that killed the dinosaurs and if the earth is flat what evidence do you have to back up the claim besides you and a ton of people saying it is