Odd One Out

At a glance 8 rules

1. 1Name the shared propertySay the rule the three share in one sentence, then find the item that breaks it. If two items break it, or none does, it is the wrong rule.
2. 2Rival properties: test eachWhen the options are properties, test each one on the other items and strike any they also have; the right one fits the chosen items only.
3. 3Numbers: check in orderTest prime or not, square or cube, then divisibility (digit sum for 3 and 9, alternating digit sum for 11), then forms like a product of two primes.
4. 4Pairs: find the linkBuild the second number of a pair from the first number n ($n^2 - 1$, $2n + 3$). For a letter and a number, n is the letter's position.
5. 5Squares: use the rootsWhen every number is a perfect square, compare the square roots instead: (9, 64, 121) has roots 3, 8, 11, and $3 + 8 = 11$.
6. 6Clusters: the inside gapsWrite the positions and the steps inside each cluster (+4, then $-2$). Ignore vowels and consonants when the question says the rule is not about them.
7. 7Mirror pairs: sum 27If three letter pairs add up to 27 (B and Y, M and N), the pair that adds up to 26 or 28 is the odd one out.
8. 8Look past the gapsIf the gaps single out no cluster, test sums: the middle letter may be the first plus the last (C, K, H is 3, 11, 8).