When Prophet Muhammad (saw) went to see heaven and hell on the night of Miraj his parents were taken out of hellfire and put in heaven. Which part of heaven was it? Was it one of the seven levels or somewhere totally different?
The OP didn't mention any evidence to the accident about taking the Prophet's (PBUH) parents out of hell and putting them in heaven, and I searched without finding any mention to that within the story telling of Israa and Miraj. However, we all know that Israa and Miraj happened before Hijrah, i.e while the Prophet (PBUH) was in Mecca and before he moved to Madinah.
So consider the following Hadith:
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَزُهَيْرُ بْنُ حَرْبٍ، قَالاَ حَدَّثَنَا مُحَمَّدُ بْنُ عُبَيْدٍ، عَنْ يَزِيدَ بْنِ كَيْسَانَ، عَنْ أَبِي حَازِمٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ زَارَ النَّبِيُّ صلى الله عليه وسلم قَبْرَ أُمِّهِ فَبَكَى وَأَبْكَى مَنْ حَوْلَهُ فَقَالَ " اسْتَأْذَنْتُ رَبِّي فِي أَنْ أَسْتَغْفِرَ لَهَا فَلَمْ يُؤْذَنْ لِي وَاسْتَأْذَنْتُهُ فِي أَنْ أَزُورَ قَبْرَهَا فَأُذِنَ لِي فَزُورُوا الْقُبُورَ فَإِنَّهَا تُذَكِّرُ الْمَوْتَ " .
Abu Huraira reported: The Apostle of Allah (ﷺ) visited the grave of his mother and he wept, and moved others around him to tears, and said: I sought permission from my Lord to beg forgiveness for her but it was not granted to me, and I sought permission to visit her grave and it was granted to me so visit the graves, for that makes you mindful of death.
The above Hadith is reported by Abu Hurairah (may Allah be pleased with him), who became Muslim in the 7th year after Hijrah. This obviously means that the prophet said that about his mother after the Israa and Miraj.
Consider the following Hadith:
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا عَفَّانُ، حَدَّثَنَا حَمَّادُ بْنُ سَلَمَةَ، عَنْ ثَابِتٍ، عَنْ أَنَسٍ، أَنَّ رَجُلاً، قَالَ يَا رَسُولَ اللَّهِ أَيْنَ أَبِي قَالَ " فِي النَّارِ " . فَلَمَّا قَفَّى دَعَاهُ فَقَالَ " إِنَّ أَبِي وَأَبَاكَ فِي النَّارِ " .
Anas reported: Verily, a person said: Messenger of Allah, where is my father? He said: (He) is in the Fire. When he turned away, he (the Holy Prophet) called him and said: Verily my father and your father are in the Fire.
Anas (bin/son of Malek) was an Ansari, i.e he lived in Madinah. He was the servant of the Prophet and was 10 years when the Prophet arrived to Madinah. This concludes that the prophet said that after the Israa and Miraj.
Since both Hadiths are after Israa and Miraj, that could tell us about the destiny of the parents of the Prophet (PBUH). However, this is still subject to disagreement and discussion among scholars, as there might be other (possibly opposing) evidence and considerations before trying to conclude a final answer about where the Prophet's parents are/will be. Everybody's destiny is, after all, beyond our knowledge. It is something that we can't be really sure about - apart from clearly foretold destines, of course, like ones told in Quran.
And Allah knows best.
It is first important to understand what the Hadith is suggesting:
The Hadith does not suggest that the Prophet's father is in Hell because of any specific crime or as an exceptional case. The Hadith is in fact making a statement about all people before the Prophet (pbuh) by giving the example of the father of the Prophet (pbuh). The statement that the Hadith is making is as follows: "people who lived in Arabia just before the Prophet's (pbuh) mission and did not believe in one God will go to Hell."
Regardless of whether, technically (i.e. on the basis of the reliability of narrators), the Hadith is correct or not, the above suggestion is against a principle that is clearly given in the Qur'an:
We read: ... your Lord would not destroy towns unjustly while their people were oblivious. - Al An'am 6:131
As it is obvious from the above, punishing people in this world who were not aware of the truth and were unmindful is considered to be an unjust act and one that the Almighty will never do. A simple analogy tells us that this is also true about punishment of Hell, that is, God will not send people to Hell if they were oblivious of the truth. On the basis of the same principle, we read: "... We never punish until we have sent a messenger" (17:15).
We then have: A Revelation of the Mighty, the Merciful. That you may warn a people whose fathers were not warned, so they are negligent. - Yaseen 36:5-6
So according to this, definitely the people in Arabia closely before the start of the mission of the Prophet (pbuh) were in principle unaware and therefore to punish them because of not believing in one God will not be just (and will not happen) unless there were individuals who knew the truth but arrogantly rejected it.
Both parents of Rasool Allah SAWS are in Paradise.
All Prophets (AS) prior to Rasool Allah SAWS were sent to their own groups and it was not mandatory for them to give daawah to others outside of their group. At times there were multiple Prophets (AS) alive during particular time. FOr example Shuaib AS and Moosa AS; Yahya AS and Eesaa AS, Lut AS and Ibraheem AS, etc.
Only our Prophet Muhammad SAWS was sent as a Prophet and Guide for the entire creation of Allah SWT.
Prior to Rasool Allah SAWS's announcement of Prophethood there was no Prophet sent to Arab area / Bani Ismaeel. After Ismaeel AS the next Prophet for that area was Rasool Allah SAWS.
In that time there were three types or group of people: 1. People who believed in Allah SWT and followed the righteous ways (deen-a-Haneef) of Ibraheem AS and Ismaeel AS 2. People who had became Idol worshipers 3. People who neither believed in Allah SWT nor did they worship Idols; essentially these were atheists.
Group 1 and 3 are forgiven and in-shaa-Allah will enter Paradise. Group 3 because of the fact that those people rejected Idol worshiping.
Evidence: Surah 17:15 Whoever attains righteousness, then he goes right only for the benefit of his ownself. And whoever goes astray, then he goes astray to his own loss. No one laden with burdens can bear another's burden. And We never punish until We have sent a Messenger (to give warning).
Rasool Allah SAWS's Parents and grandfather are amongst group 1. They did not commit Shirk!
Group 2 on the other hand will enter hellfire. Evidence: 4:48 Indeed, Allah does not forgive association with Him, but He forgives except that (anything else) to whom He pleases, and whoever sets up partners with Allah in worship, he has indeed invented a tremendous sin.
And Allah SWT knows best