As far as Superman being cloned, Pre-Crisis Cadmus did crack Superman's DNA like they did with Olsen and could be cloned. In Superman's Pal Jimmy Olsen #136, Superman said that it was his cell tissue that was first grown there when they broke and deciphered his genetic code. That's why it made perfect sense for the Post-Crisis Cadmus to be the ones to create the Post-Crisis Superboy. There was a lot of Kirby in Superboy's origins and it's funny how many tributes to Pre-Crisis Kirby were in Superboy even before his series started (Auron being a tribute to Arin the armored man, etc.). NOWHERE isn't even close (and they screwed up Project Cadmus so many times....from "Cadmus Labs" to not even being close to what they were before).
The Evil Factory with Symian and Mokkari also cloned Superman Pre-Crisis (Jimmy Olsen #135) and Post Crisis (created a flawed clone made from Kryptonite affected cells). Post Crisis Lex couldn't even clone anyone let alone himself without help from two top scientists doing the work (Teng and Donovan).