The theme is the main subject that you are going to write about in a essay or in a report. If you want to know more, just ask :)
1) Find from the given dialogue the opposites of :-
(I) Little = <u>more</u>
(II) Reject = <u>accept</u>
(III ) Start = <u>end</u>
(Iv) Innocent = <u>guilty</u>
I would say that the lines from Antigone that show a result of Creon's change in fortune, or his peripeteia are:
Second messenger: Thy [Creon's] wife, the mother of thy dead son here,
Lies stricken by a fresh inflicted wound.
As a result of his change in fortune, both his wife and son are dead.
They couldn't find it because they were not worthy. Only Galahad could find it and he did because he was deemed worthy and is the greatest knight ever. He's the son of Lancelot and because he's so pure and honorable he was able to find it, or let's say the grail allowed him to find it.