And He is Allah, There is no god but He

What is the meaning of His (SWT) saying: {And He is Allah: There is no god but He. To Him be praise, in the first and in the last: and His is the Command(Judgment), and to Him you shall be brought back}

Grand Ayatollah – Grand Sign of Allah

A lot are named (Grand Ayatollah – Grand Sign of Allah) with the recent scholars, so what is the meaning of ‘Grand Ayatollah’? And is it specifically (only) for the Imams (pbut) or for everyone in order for all of the scholars to be called by it (rightfully)?