Let's see this in the light of Qur'an and Ahadith:
Does Hell consist of 7 levels:
It has seven gates; for every gate is of them a portion designated."
لَهَا سَبْعَةُ أَبْوَابٍ لِّكُلِّ بَابٍ مِّنْهُمْ جُزْءٌ مَّقْسُومٌ
This verse suggests: No. It has seven gates and every gate has God knows how much levels.
What does quran say about this?
As @Ali have mentioned, there are many verses suggesting that Christians/Jews can go to heaven:
Surely those who believe, and those who are Jews, and the Christians, and the Sabians, whoever believes in Allah and the Last day and does good, they shall have their reward from their Lord, and there is no fear for them, nor shall they grieve.(2:62)
Surely those who believe and those who are Jews and the Sabians and the christians whoever believes in Allah and the last day and does good-- they shall have no fear nor shall they grieve.
These two verses suggest that the only condition is believing in God and judgement day.
In addition we have this verse:
So whoever does an atom's weight of good will see it, And whoever does an atom's weight of evil will see it. 99/7-8
This verse doesn't say: Muslims who do good will see it, it says whoever.
At last, I would say that this is a very complex issue, we can't answer it by
All x group will go to heaven/hell.
To show the complexity of this issue, let me clarify some points:
It is possible for people to go to hell then go to hell: In fact, most(all?) people will go to hell but the difference is in the time people will remain there.
And there is none of you except he will come to it. This is upon your Lord an inevitability decreed.
Then We will save those who feared Allah and leave the wrongdoers within it, on their knees. 19:72
This verse doesn't say that Allah will save Muslims, it says he will save those who fear him.**
2. It is possible that two people, doing the exact same thing one to go to hell and the other to heaven.
You ask: how?
This is due to many reasons:
Whoever should desire the immediate - We hasten for him from it what We will to whom We intend. Then We have made for him Hell, which he
will [enter to] burn, censured and banished.
But whoever desires the Hereafter and exerts the effort due to it while he is a believer - it is those whose effort is ever appreciated
[by Allah ].
To each [category] We extend - to these and to those - from the gift of your Lord. And never has the gift of your Lord been
restricted. Look how We have favored [in provision] some of them
over others. But the Hereafter is greater in degrees [of difference]
and greater in distinction.
Knowledge and brain:
For example Allah wouldn't treat a philosopher the same as he treats a 6 year old boy for example. Because the first has the knowledge to show him the difference between good and bad while the other doesn't.
There are many examples that I can't cover in the answer. The important thing is to know that there are people who will go to hell and people who will go to heaven and work to be with the latter.