To contextualize my question, I'm going to tell you what I'm not asking: Im not asking for proof of Ismah as a doctrine, but rather why Prophets have been given ismah in the context of predestination and free will. Moreover, I am not asking for proof of free will either.

My question is in multiple parts and I've done my best to break it down into yes/no type questions. okay, Bismillah.

Were Prophets chosen from the start or were they chosen conditional to whether someone in a society was capable of accepting Prophethood (by their own merit)?

If the former, then can't the objection be brought up that those prophets were essentially predestined heaven (and therefore making Allah unjust in some way)?

If the latter, then is it possible for ordinary people to reach the level of prophets?

If this is not possible and if what makes prophets better than ordinary humans the fact that Allah has granted them wahy and knowledge, then is it fair ask why ordinary people don't also receive that same treatment as mentioned by 12:24 which would thereby guarantee them heaven and protection from sin?

If the granting of wahy and knowledge is conditional upon someone having intelligence and purity, then is it a reasonable objection to say that intelligence is not a controllable factor?

If intelligence is not a controllable thing, then can the same objection be brought up that most intelligent people who are granted prophethood are guaranteed heaven (thus making Allah unjust again) because their uncontrollable faculty of reasoning was why they were granted wahy which prevents them from sin? (That is, someone's uncontrollable circumstances has led them to have a higher capacity, and therefore they have a greater opportunity to reach a higher level of heaven than ordinary people)

Please forgive the scatterbrained question, I had to think about how I was going to ask this. I'm not sure if you can ask for clarification on this app, so forgive any confusing wording.

First of all I would like to appreciate you your question is very important and genuine so don’t worry about that.
As you asked it’s true that Allah (swt) has given special grace and grade to His Prophets and Imams too because of two major reasons:
1- No doubt that Allah (swt) has created our soul before our body ( I.e everyone’s soul has created before their material body in this very world)
وَإِذْ أَخَذَ رَبُّكَ مِن بَنِي آدَمَ مِن ظُهُورِهِمْ ذُرِّيَّتَهُمْ وَأَشْهَدَهُمْ عَلَىٰ أَنفُسِهِمْ أَلَسْتُ بِرَبِّكُمْ قَالُوا بَلَىٰ شَهِدْنَا أَن تَقُولُوا يَوْمَ الْقِيَامَةِ إِنَّا كُنَّا عَنْ هَٰذَا غَافِلِينَ

And when your Lord brought forth from the children of Adam, from their backs, their descendants, and made them bear witness against their own souls: Am I not your Lord? They said: Yes! we bear witness. Lest you should say on the day of resurrection: Surely we were heedless of this.(7:172)
Therefore when all of us have given this testimony “” Am I not your Lord? They said: Yes! we bear witness.””.
It means we all have been tested by Allah (swt) in Aalam e Zarr.
What Allah has tested us and do all of us received the same Rank or grade or position after that testing ??? If we say Yes then we can get objection or oppose that why Allah has selected few personalities amongst all Humanity as a Guide for rest of the Human.
Also It’s very clear near Allah’s absolute Knowledge who is going to show his ability in the world of Practical life according to His wish and will ( Make sure Allah has give all of us same free will as prophets have without fraction discrimination)
Example: when a father sends his two children in same school and takes care of them in same way and nurture them in same style but when it comes to his knowledge that one of them is more capable and has more grasping power of understanding knowledge then he starts paying more attention towards this particular son. Is this called as favour or discrimination or it has to be called that because his one child showed more ability so he deserves more attention otherwise all his ability will go in vein?
Therefore if we see amongst all His creations Allah has selected few of them as His special successor or Khalifa it’s because they showed their ability while in their life of Aalam e Zarr ( i.e the life before getting material body)

Note :what I said above It has been mention in the Dua of Nudba and in many more Ziyarats and traditions of Aimmah and Prophet (saww)

2- If Allah has given special authority and position to few of His servants to serve Humanity, its not only any called as favour them rather it’s a great favour to the rest of the Humanity. Why because if you see the very goal and purpose of our creation in this material world we strongly in need of a personality to whom we could follow as Allah desires from all of us.
3- If you see the life of all those Prophet and even our 12 Imams you will never find any smallest fault due to their worldly desires that they have committed any action which was against the will and wish of Allah. “”( Note: Tarke Awla (leaving most appropriate ) from few Prophets is an another topic of discussion””
But none of the Prophet had a fraction desire to achieve worldly pleasure despite having the same quantity of Desires like other humans have. But they sacrificed all their wish and desires in front of Allah’s Will and Wish. But at the same time if we can find any other personality completely same as what Prophets have sacrificed in their life and he didn’t get a place of Nubuawa then we can say that why Allah has selected those one as His Nabi and revealed His Wahi (revelation) upon them. We believe 124,000 Prophet and all Prophets have their successor and their Successors have their either disciples or companions and all of them did their Job well and all they have great reward near Allah. But in our daily life or some times in one’s whole how many people we have seen that they had the same qualities as a Prophets have?
Lastly as for as our resurrection and reckoning on the Day of Judgement concern Allah says in the Holy Quran:
لَا يُكَلِّفُ اللَّهُ نَفْسًا إِلَّا وُسْعَهَا لَهَا مَا كَسَبَتْ وَعَلَيْهَا مَا اكْتَسَبَتْ رَبَّنَا لَا تُؤَاخِذْنَا إِن نَّسِينَا أَوْ أَخْطَأْنَا رَبَّنَا وَلَا تَحْمِلْ عَلَيْنَا إِصْرًا كَمَا حَمَلْتَهُ عَلَى الَّذِينَ مِن قَبْلِنَا رَبَّنَا وَلَا تُحَمِّلْنَا مَا لَا طَاقَةَ لَنَا بِهِ وَاعْفُ عَنَّا وَاغْفِرْ لَنَا وَارْحَمْنَا أَنتَ مَوْلَانَا فَانصُرْنَا عَلَى الْقَوْمِ الْكَافِرِينَ

Allah does not impose upon any soul a duty but to the extent of its ability; for it is (the benefit of) what it has earned and upon it (the evil of) what it has wrought: Our Lord! do not punish us if we forget or make a mistake; Our Lord! do not lay on us a burden as Thou didst lay on those before us, Our Lord do not impose upon us that which we have not the strength to bear; and pardon us and grant us protection and have mercy on us, Thou art our Patron, so help us against the unbelieving people.(2:286)
Therefore all of us will be questioned and be rewarded according to our own ability.
According to the tradition Prophet Suleiman will enter in to the Heaven after all Prophets have already entered. Why because Allah has given him power and authority over His all creatures and made him a great King so he will be questioned more in comparison to other Prophets.
I hope I have given your answer Allah knows better but still you have right to ask if you need.