First ??? quest: Get an orange potion (to get the Firefox costume)

Second ??? quest: Enter a portal. I found one to the east-southeast to the starting point.

Still trying to figure out the last one.

The last one is Rickroll'd, you meet Rick Astley in one of the caves.

It's in the maze, I've heard, but I can't find Rick.

The easiest way is, pick a random door in the first room, and then every time you come into a new room go back the way you came (doors aren't symmetric in this game.) This will put you in a cycle that eventually takes you to Rick. You'll visit some rooms more than once.

Alternately, just stumble around until you find a room with one top entry and 3 bottom entries. Take the bottom left door, which will take you to Rick.

He's in there. Try unorthodox combinations. I think there's some state stored on whether or not you went through "up" doors or "down" doors.

Always go to the left, even if it's the entries to the top or the bottom.

I did both but didn't get any additional achievement, what am I doing wrong?

It's in the cave above the cat.