Does anyone have a full explanation of the riddle in The Cursed Child

Question

In Harry Potter and the Cursed Child there is a riddle. While I can get a lot of it (indeed, a fair amount of it is explained by the characters themselves), I'm less confident about other bits, particularly the last third of the riddle. So, does anybody have a complete breakdown of the riddle?

The first is the fourth, a disappointing mark
You'll find it in parked but not in park.

The second is the less fair of those that walk on two legs.
Grubby, hairy a disease of the egg.
And the third is both a mountain to climb and a route to take.

A turn in the city, a glide through a lake.

(Harry Potter and the Cursed Child - pp.89-90 - Little, Brown - Act One, Scene Nineteen)

Answer 1

De

• The first is the fourth [letter of the alphabet], a disappointing mark [D for Dreadful]

• You'll find it in parked but not in park = [Self-explanatory. The letters D and E are not found in the word park]

Men

• The second is the less fair of those that walk on two legs = Women are known as the fair sex. Men are, by intimation the less fair.

• Grubby, hairy, a disease of the egg = [Hermione is suggesting that the eggs which result in male births are diseased].

Tors

• And the third is both a mountain to climb [Another word for a mountain is a 'tor]' and a route to take [as in 'guided tours'].

• A turn in the city, a glide through a lake = [These just seem to be examples of places on which you could be taken for a guided tour].

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DELPHI/HERMIONE (effusively): Men! De-men . . . tors. We need to find a book on dementors. (The bookcase pulls her in.) Albus!

ALBUS/RON: Delphi! What is going on?

SCORPIUS/HARRY: Concentrate, Albus. Do what she said. Find a book on dementors and be very careful.