It replaces any fusion material as long as it's not specific, and it says there a "synchro spellcaster", so no. You can use a synchro spellcaster and king of the swamp though.
"This monster can only be Special Summoned by Fusion Summon (from the Extra Deck)." So yeah. Can't do that either. Unless Light Hex said its effect is treated as a fusion summon.
Neither of these are specific. A specific Fusion/Synchro/XYZ Material is given by "..." with the name of the card. "King of the Swamp", or any Fusion Substitude Monster, cannot be used in order to Fusion Summon "Supreme Arcanite Magician".
XraishionX was correct, regarding "The Light - Hex-Sealed Fusion".
Anything else? This needs to get locked before getting more spam that doesn't make any sense at all..
All fusion substitutes, as a rule, can't be used if the cards are not named specifically, but in this case it is. Supreme clearly says "a synchro", but of course you had to give attitude and pretty much agree with all the answers but pretend you are a badass. How unprofessional for a teacher.