@iceman
Ma sha Allah, you have at least answered my questions which was more than I was expecting. Briefly, I will say here that despite having answered the questions, your answers reveal how you are playing games and have departed from the position of your own Twelver madhhab:
Allow me to explain. Please pay attention and acknowledge.
"Does this mean you accept the authority of the Khalifat ul Muslimeen, I mean the institution which was created from Saqifa?"
You have two things here, 1, Religion (Deen). 2, World (Dunya). To break it down further you have religious authority, which is divine authority as well as authority chosen by election selection of the people. These are two different authorities.
This right here is the standard Sunni position. We recognize a distinction between religious and secular authority. Religious authority is wielded by Prophets alone, while secular authority may be exercised by figures that have no religious authority (i.e. the caliphs). A Prophet may also exercise secular authority but that is not always necessary.
Now you have departed from the Twelver madhhab which says that the exercising of all authority such as the government is the sole right of the Infallibles, meaning the Prophet and the 12 Imams. They make no distinction between religious and secular authority.
Otherwise, why do all the Shia object to the secular authority of sayyidina Abi Bakr RA as the Prophet's first caliph, when he only exercised secular authority and not religious authority, nor did he ever claim his authority is essentially religious?
Why could not the Shia be content with saying that their madhhab is that sayyidina Ali RA was the Imam in Religion and Abu Bakr RA the caliph in secular authority over the Ummah and that the latter was valid?
When they invalidate the latter it means they do not recognize a distinction between religious and secular authority.
If you say that sayyidina Ali RA was indeed the Imam in Religion but he should have also been the caliph of secular authority because he was most qualified for the task and not because he had a religious divine authority to be the caliph of secular authority, then you have departed from the Twelver madhhab's position. The Twelvers say that sayyidina Ali RA had the divine authority to be the caliph of the Muslims, meaning rule them in the dunya not simply the Deen.
For example Muhammad s.a.w was a Messenger and Prophet. He was divinely appointed. Why didn't the Muslims just accept and keep him as a religious guide and gather to elect and select a leader to run the world affairs? Ever thought of that?
What do you think the people of Medina did? Even the Jews of Medina accepted Prophet Muhammad صلى الله عليه وسلم as their ruler, chief and judge but in dunya not deen. In addition to being a Prophet of God, sayyidina Muhammad صلى الله عليه وسلم was in a position of judge over Medina. That is why the Jews would come to him to settle their legal disputes and refer to him for judgment. They agreed to the Charter of Medina which was like a constitution describing the political setup of Medina. The Jews accepted him as a judge but not as a Prophet. He صلى الله عليه وسلم became the judge and ruler of Medina by the agreement of the people of that town, both Muslim (Ansar) and non-Muslim (Jewish clans).
In fact, at times the Prophet صلى الله عليه وسلم even delegated this secular authority of his to others. For example, the appointment of sayyidina Saad b. Muadh رضى الله عنه to act as judge in the matter of the treason of Bani Qurayza. Before giving his judgment, sayyidina Saad b. Muadh even confirmed that the Prophet too would be bound by his judgment, because it was a secular matter not a matter of Deen. When sayyidina Saad b. Muadh arrived, the Prophet صلى الله عليه وسلم stood up and instructed the Ansar to stand up قُومُوا إِلَى سَيِّدِكُمْ "Stand up for your Master". This was to acknowledge Saad b. Muadh's secular authority.
Now how can a Prophet delegate religious authority to one of his companions, that too someone whom you don't consider to be Ma'sum? It was obviously the delegation of secular authority which is not divinely appointed.
When it comes to Muhammad s.a.w he is the religious leader as well as looking after the affairs of the Muslims and the world. But after Muhammad s.a.w religion and religious authority is restricted to only Muhammad s.a.w and the Qur'an and we need to elect and select someone else to run the affairs of the Muslims and the world?
Now I've answered this point. The secular authority of Prophet Muhammad صلى الله عليه وسلم was not divinely appointed. Even the Jews of Medina acknowledged his secular authority and treated him as a judge to settle their legal disputes. The people of Medina agreed to have him as their secular leader, he was not divinely appointed to that position.
Point 2, obviously Muhammad s.a.w didn't name and appoint anyone to govern after him because either there was no need to or he just simply didn't bother. I wonder why.
Just as the Prophet صلى الله عليه وسلم attained his position of judge and ruler over Medina by the agreement of her people, he expected his own Sahaba to consult and elect a leader among themselves, hence why he never designated any successor, though of course there are Hadith where he predicted who would succeed him and where he hinted at the fact that Abu Bakr RA should succeed him, hence why he appointed him to lead the prayers in his final illness.
Now the answer to your question,
NO we do not accept the authority of "Caliphatul Muslimeen' as a religious authority because we believe in divine authority and a divine leader just like Muhammad s.a.w.
Neither do we. We believe that religious authority has ceased in the person of Prophet Muhammad صلى الله عليه وسلم. You acknowledge that the institution of Khilafa is a secular institution and does not wield religious authority. The only thing is that you are acknowledging a parallel institution, which you consider divinely appointed, namely Imamate.
According to you, this divinely appointed institution can exist side by side with the secular caliphate. My question is do you consider the caliphate as a secular institution valid? If you say yes you have departed from the Twelver madhhab. If you say no, then you have to answer why historically your Imams (Ali, Hasan and Hussain رضى الله عنهم) did not revolt against the caliphate. You also have to answer why Ali and Hasan رضى الله عنهما accepted the office of caliphate, and why sayyidina Hasan رضى الله عنه subsequently resigned from that institution knowing full well it would then be occupied by Mu'awiya رضى الله عنه?
But we have to accept and consider that Muslims took a different turn and developed a man made and selected authority of Caliphatul Muslimeen. In history whether one accepts or not likes or not the title and authority of Caliphatul Muslimeen was created and started.
The point is you say it is wrong and an error for the Muslims to have done this. By saying so, you automatically posit that this institution must be divinely appointed.