>>1015973
>Red sunlight robs him of his extraneous powers and weakens him to the level of a normal human with the same muscular density. He feels sluggish and weak because he's not used to actually using his muscles
No. In Superman #141 "Superman's Return to Krypton", Superman #164 "The Showdown Between Luthor and Superman", and Action Comics #300 "Captive of The Red Sun", Superman is able to move around just fine under a red sun. The real problem is Superman is so conditioned to having super-powers that he holds himself back from using his full strength when caught in Red Sun situations. For example, in "Showdown", Luthor nearly beat Superman to death because Superman was pulling his punches.
>Did kryptonite, being chunks of the exploded planet Krypton, have an impact on the lives of Kryptonians before its destruction? Are all pieces of planet Krypton kryptonite, or is it a particular mineral found on Krypton?
No. Kryptonite was only formed after the explosion of Krypton. The catastrophe apparently caused a chain reaction in the material that made up the planet which made it deadly to the planet's inhabitants. This chain reaction occurred with all pieces of Krypton, as was the case for the Domed City of Argo. Argo miraculously survived Krypton's destruction, only for the ground it was attached to become Kryptonite.
>Are the various colors of kryptonite all variations of the same mineral (ruby and sappire are both corrundum, for instance) or different minerals?
Yes. All colors of Kryptonite are the same element, but each has been chemically changed in one way or another, making their effects on Kryptonians different. Red Kryptonite, for example, passed through a mysterious Crimson Cosmic Cloud, making it unstable and having a completely random affect on Kryptonians.
>If the Kryptonian race is spacefaring, as implied by some writers as well as the Supergirl TV show, why are there so few survivors of the planet's death?
In the Silver Age, the only things Kryptonians shot into space were criminals and dangerous things they didn't want on their planet. This practice ended when the criminal scientist Jax-Ur used a rocket to destroy the inhabited moon of Wegthor. This crime brought all Kryptonian space operations to an end and prompted the creation of the Phantom Zone as way to imprison criminals, with Jax-Ur being its first first inmate.