Round 2

2. O, P, S, T work. opts, post, pots, spot, stop, tops.

3. Number of letters in the number written out plus number itself, e.g.
o-n-e: 3+1=4
t-w-o: 3+2=5
t-h-r-e-e: 5+3=8
etc.

50th = 55
63rd = 73
100th = 110

4. J-P between I and Q
B-S between A and T
G-V between F and W
N-Z after M
P-R between O and S
F-L between E and M

5. A common mistake people make with this puzzle is assuming that Carl was being disobedient. It was made clear that he is very obedient. If he complained about something, it is because he thought he was supposed to.

The sign said "Refuse to be put in the bins provided" or something to that effect. Carl simply misinterpreted the word "refuse", and did not realise it was a synonym for garbage.