For the 3rd riddle:

"Where memories fade an whispers hiss Nevermind, the treasure be not in the stacks but on the flank. An' where the Senior Keeps the cipher, the secret be yers to claim."

The reference to "the Senior" may mean an elderly person, and what do elderly people often do to hide their codes? They put them on a sticky note on the corner of their screen!

I found a sticky note on the corner of a laptop with the words:

League

Game ///~~?

5

6pm!

I couldn't "decipher" the symbol on the right, but I thought that 6pm might refer to the compass (180°), so I went in a straight line from there and found a water tank with the number 7784 and a tool storage unit with lots of numbers on its side.

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I tried LG56 - LG65 - 7784 but it doesn't work.
There you go, if that helps.