Is the chassis of the Mercedes-Benz R-Class the same as that of the S-Class?

Not the same. The corresponding chassis of the Mercedes-Benz S-Class includes W221, W220, W140, and W126, while the corresponding chassis of the Mercedes-Benz R-Class is W251, so the chassis of the Mercedes-Benz R-Class is different from the S-Class. Mercedes-Benz is a world-famous luxury car brand. In January 1886, Karl Benz invented the world's first three-wheeled car and obtained a patent. He is known as the "inventor of the automobile."