What is the rhyme pattern of the sonnet of the poem Ozymandias. what are the themes of the octave and the sustet. is their any distinction between the two that fed?

The rhyme scheme of Shelley's Ozymandias is: ABABACDC ECE FEF. For extra merit you could point out that the poem starts like a Shakespearean Sonnet, but ends as three triplets of TERZA RIMA (a rhyme pattern common in Italian, but very rare in English; Shelley spoke fluent Italian). It is debatable whether the poem has a sestet. If your teacher insist on seeing a sestet, then the theme of the Octave is the current appearance of the Statue of Ozymandias (Ramases II), while the theme of the Sestet is the 'meaning' the statue is given:- first by the inscription on its base, and then by the current ruinous nature of both the statue and its surroundings. But for extra merit, you could point out that there are really TWO Volte (changes of theme). Lines 9-11 show the meaning that the statue was intended to have (an image of a mighty conqueror), lines 12-14 show the statue's final meaning (a ruin of a forgotten despot). It's a tricky poem, and will repay as much study as you are willing to give it.