Four "cosmetic" questions

On October 4, 1957, the Soviet Union launched the Earth's first artificial satellite, Sputnik, into orbit using a Semiorka rocket. Once orbit has been reached and Sputnik released, while the first and second stages immediately fall back to earth, the third stage and fairing, now useless, remain on the same space trajectory as the satellite, becoming the first piece of space debris. Between them, they weighed over 6,500 kg, whereas Sputnik weighed just 84 kg: the payload represented just over 1% of the mass injected into orbit. After emitting its famous "beep beep" for 21 days, Sputnik remained in orbit for a further 92 days, before re-entering the atmosphere and burning up. At this point, the world discovered that it was impossible to travel into space,...