Is it valid to cite His saying, exalted be He: "His command, when He intends a thing, is only that He says to it, 'Be,' and it is," as evidence that if Allah had willed the imamate for Ali ibn Abi Talib, he would have been an Imam, and does this fall under the universal-predeterministic will or the religious-legislative will?

The will of Allah is of two types: A universal, preordained will (mashī'ah) which must come to pass, and a religious, legislative will (maḥabbah) which may or may not come to pass. We believe that Allah willed the Imamate of Ali both legislatively and universally. He is the fourth of the Rightly Guided Caliphs after the Messenger of Allah, peace and blessings be upon him, who are Abu Bakr, Umar, Uthman, and Ali. The hadiths indicate their caliphates, and that the duration of the Prophetic Caliphate is thirty years. Safinah mentioned that this period includes the caliphates of Abu Bakr, Umar, Uthman, and Ali, and calculations have shown that the sum of their caliphates completes the thirty years.