Elbow-licking: Inside yes, outside no.
Thank you for including Garfield Goose on the list!
Non-green pinching: That was very popular when I was in grade school (Michigan, early-mid '60s), but I haven’t seen or heard it since.
“I will give this sack of doubloons to [whoever quacks most convincingly like a duck].” It’s the subject of that clause, and the entre clause is the object of the preposition.
Pi: 20. Sir, I send a rhyme excelling, / In sacred truth and rigid spelling, / Numerical sprites elucidate / For me the lexicon’s dull weight.
Otters: Which one(s) do you have in mind? Per Wiki, “The 13 species range in adult size from 0.6 to 1.8 m (2.0 to 5.9 ft) in length and 1 to 45 kg (2.2 to 99.2 lb) in weight.” But no matter which one(s) you pick, the answer will be more than 100.