Answers to the special no-theme trivia quiz...
1. How did Mon-El make Element 152?
Mon-El was shown making it in Adventure 305. From his speech balloon: "Swiftly, while concentrating mightily, I super-rub the block... thus rearranging its molecules so that Element 152 is created, an element which never before existed on this planet! You see, the atomic weight of gold is 79... silver is 47, and iron is 26! Add them up together - and the total is 152 - a new element..." (ellipses verbatim). No, really, it's he manually performed nuclear fusion on gold, silver, and iron without killing everyone. See the 30th century rare elements page.
2. Which Legionnaire(s) appeared on the covers of all three Legion Sourcebooks from Mayfair?
Only Ultra Boy appeared on the Legion Sourcebook vol 1 (Mayfair #213), vol 2: The World Book (Mayfair #216), and the 2995 Sourcebook (Mayfair #263).
3. What is inertron made of?
I'm pretty sure it was never explicitly explained in the comics, but according to the Legion Sourcebook vol 2 (page 71), inertron is "an alloy of 20 parts titanium to 1 part dwarf star metal". I'm not even going to try to work that one out.
4. Who were the Legionnaire counterparts to the Legion of Super-Rejects?
The Rejects were Micro Lad, Magno Lad, Esper Lass, Calorie Queen, Phantom Lad and Chameleon Kid, so their counterparts were Shrinking Violet, Cosmic Boy, Saturn Girl, Matter-Eater Lad, Phantom Girl, and Chameleon Boy. (This was my very first-ever Legion issue, by the way.)
5. Which Legion villains have been related to each other?
Hunter and his son Otto Orion; Jungle King and his brother Marden King; Lars "Starfinger I" Hanscom & Molock the Merciless; Charma, Grimbor, and their daughter Charma II; Tharok and his clone the Dark Man; Lightning Lord and his nephew Validus; GDS Darkseid and his Orion Servant of Darkness; L2 Darkseid and his older self; and, since I'm allowing clones, the various members of the Dark Circle.
IDLE suggested Lex Luthor and his descendant, and Mr. Mxyzptlk and his descendant, but in the Adult Legion both 30th century descendants were good guys. There was another evil Mxy, true, but the original is not a Legion villain.
6. Which Legion-related character was inspired by Tom McCraw?
From the June 7, 1996 LSH AOL chat report (back in the days when we had a weekly chat on AOL with various Legion creators):
Atom'x--who appeared in LSH #82--was intended to be a preboot character named Atmos, but a switch was made in production. The switch was made because Lee Moder drew the character incorrectly. Tom stresses that the mistake was not Lee's fault. The mistake was not caught until after the book had been inked, and it was faster to create a new character rather than redraw the book.
Tom Peyer used the Atom'x name--which is based on Tom McCraw's screen name [ATOMC]--without McCraw's knowledge. McCraw vows revenge, and promises that the revenge character will wear pink or pastel purple. Tom did not know that the character would be named after him when he was coloring the character.
7. How many domed cities made up New Earth following Earths' destruction in v4?
The 2995 Sourcebook (page 171) says that there were 94 domed, linked cities that made up New Earth.