They are probably tournament legal in old school (cards printed in 93/94 which I play with my son) and in something called Vintage.

With multilands you must mean the Dual Lands and they have a lot of value. https://www.mtgstocks.com/lists/6 - even if they are from the revised set and have been played with we speak about at least $200 each and you probably had 20 or so in your deck.

If by original editions you mean Alpha (black border, round corners) and Beta (black border) - they have insane value depending on which cards of course.

Do you remember if the cards had black borders? Would love to see some photos of your deck :)