On-sale date from copyright registration.
Per Gene Reed, Jack Schiff once remarked that he sometimes used Sprang's splash page for the cover and then used the original cover for the splash or had another splash drawn, and suggested that that appears to be the case here. Based on that bit of information, Jim Van Dore suggests the Lois Lane figure was added by Curt Swan when the cover and splash were swapped in this case. Letters credit from Todd Klein via his Klein Letters blog (18 September 2016, http://kleinletters.com/Blog/ira-schnapp-in-worlds-finest-comics-part-1/).
1st meeting of Bruce Wayne and Clark Kent in Smallville.
Green Arrow wears a red hat. Arrow Cave called Secret Lair.