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The five key numbers were 13, 9, 15, 14 and 19

We worked out the first puzzle by observing a 3D dice and by calculating the top from the bottom, to add up to 7.
We worked out the second puzzle by triying lots of different combinations, until we found the correct answer.
To find the awnser to key number 3,we worked out the diameter and subtracted it from the length of the rectangle.
We did thne same as number 2 for key number 4.
For the last one we looked for a number that was a multiple of 5 plus and that it was also a multiple of 4 plus three which happened to be 19.
So to exit the castle we had to find out Skippy's real name;so we did S=13,I=9,
M=15,O=14,N=19.
SO THEREFORE HIS NAME MUST BE SIMON!