They practice against other sumo wrestlers. Each stable has one or more trainers that will help them work out. Often they will lift weights or push against posts.
more than you think
Sumo wrestlers tend to carry a lot of mass, to make them more difficult to move and throw.
more than 500,000 dollars per year
It depends on which wrestler and UFC fighter you are comparing. Actually speaking the top wrestlers like "John Cena" or "CM Punk" or even part time wrestlers like "Rock", "Brock Lesnar" or "Undertaker" make far more money than almost all the UFC fighters. Similarly, the top UFC fighters like Anderson Silva, Jon Jones etc make more money than most of the wrestlers. In fact, the amount of money these guys make is a direct reflection of their popularity and the guys who are champions usually make more money than the rest of their peers.
Because they have more experienc and are a bigger draw
Ramses made egypt more stable by being a ruler for 66 years
They make the ball more stable and aerodynamic.
This depends on the sumo wrestler and wrestler in question. However, it can generally be agreed that sumo wrestlers are stronger. (However, many recreational/amateur sumo wrestlers are not strong)
quechua
adding one more electron
Mitosis