What is the evidence for the correctness of the Sunni view that the caliphate is by consultation (shura), or the Shiite view that it is by divine designation (nass)? And is it true that the Sunnis were unable to identify the twelve Imams mentioned in Al-Bukhari?

The Sunnis differed on whether Abu Bakr's caliphate was based on a divine text (nass) or consultation (shura). The Shias, on the other hand, disputed Abu Bakr's leadership, claiming that the Prophet (peace be upon him) explicitly designated Ali for the caliphate, citing evidence that is neither authentically transmitted (naqlan) nor sound in reasoning (nazaran).

As for the Hadith (definition) of the Twelve Caliphs, the Sunnis have explained and clarified it, and it has no connection to what the Shias believe about their Imams.

Scholars have differed in identifying the Twelve Caliphs. One of the most preferred opinions is that they existed during a period when the Caliphate was strong, Islam was powerful, its affairs were upright, and there was consensus on those who assumed the Caliphate. These are Abu Bakr, Umar, Uthman, Ali, Mu'awiya, Yazid, Abd al-Malik ibn Marwan and his four sons (al-Walid, Sulaiman, Yazid, and Hisham), Umar ibn Abd al-Aziz, and al-Walid ibn Yazid ibn Abd al-Malik.

It was also said that they are from Abu Bakr (al-Siddiq) to Umar ibn Abd al-Aziz, meaning twelve individuals, excluding those whose rule was not valid or whose term was not long, such as Mu'awiya ibn Yazid and Marwan ibn al-Hakam.