For no. 2, FluidnMotion got the one that I was thinking of, but Nona gave an interesting variant and I accept Clive's explanation.
For no. 1 the "correct" answer was "That that is is; that that is not is not. Is not that it? It is", as Benita put it. I'm not so convinced by Benita's "b" solution.
A couple of points here: Benita puts "that that is
, is". Perhaps the comma makes it clearer but I'm not sure that it can be justified grammatically because it means putting a comma between the subject and the verb. You can say "My cat, which I love, eats fish", but you would not put just a comma as in "My cat, eats fish".
The other point is about "Is not that it?", even though I included it myself. The contracted interrogative negative is "isn't that it?", but maybe the uncontracted form should be "is that not it?". It's such an unusual form that I don't know which sounds natural and I can't be bothered to look it up!