Academic Dishonesty what it is and what it isnt

[Studentofdeed]

I wanted to ask your guys opinion on this topic. Is cheating during an exam a sin? What constitutes cheating? Say a friend took an exam before and he gives you advice about it? Is that cheating? Students who took a class before sharing past exams or mateiral...is that cheating? Is looking up stuff during an online exam considered cheating? Some professors do not care and some do? Please give guidelines so I may not make this mistake again. Am I supposed to confess to professor if I was involved with one of the steps above?

[Studentofdeed]

One of my professors flat out told us that He doesn’t care if we chest on his test but rather he calls a it a skill of collaboration. Im confused...Im scared if I commited a grave sin and how should I repent?

['Abdullah]

Narrated Abu Hurairah:
That the Messenger of Allah (ﷺ) passed by a pile of food. He put his fingers in it and felt wetness. He said: 'O owner of the food! What is this ?' He replied: 'It was rained upon O Messenger of Allah.' He said: 'Why not put it on top of the food so the people can see it?' Then he said: 'Whoever cheats, he is not one of us.'"
He said: There are narrations on this topic from Ibn 'Umar, Abu Al-Hamra', Ibn 'Abbas, Buraidah, Abu Burdah bin Niyar, and Hudhaifah bin Al-Yaman.
[Abu 'Eisa said:] The Hadith of Abu Hurairah is Hasan Sahih Hadith. This is acted upon according to the people of knowledge. They dislike cheating and they say that cheating is unlawful.

حَدَّثَنَا عَلِيُّ بْنُ حُجْرٍ، أَخْبَرَنَا إِسْمَاعِيلُ بْنُ جَعْفَرٍ، عَنِ الْعَلاَءِ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم مَرَّ عَلَى صُبْرَةٍ مِنْ طَعَامٍ فَأَدْخَلَ يَدَهُ فِيهَا فَنَالَتْ أَصَابِعُهُ بَلَلاً فَقَالَ ‏"‏ يَا صَاحِبَ الطَّعَامِ مَا هَذَا ‏"‏ ‏.‏ قَالَ أَصَابَتْهُ السَّمَاءُ يَا رَسُولَ اللَّهِ ‏.‏ قَالَ ‏"‏ أَفَلاَ جَعَلْتَهُ فَوْقَ الطَّعَامِ حَتَّى يَرَاهُ النَّاسُ ‏"‏ ‏.‏ ثُمَّ قَالَ ‏"‏ مَنْ غَشَّ فَلَيْسَ مِنَّا ‏"‏ ‏.‏ قَالَ وَفِي الْبَابِ عَنِ ابْنِ عُمَرَ وَأَبِي الْحَمْرَاءِ وَابْنِ عَبَّاسٍ وَبُرَيْدَةَ وَأَبِي بُرْدَةَ بْنِ نِيَارٍ وَحُذَيْفَةَ بْنِ الْيَمَانِ ‏.‏ قَالَ أَبُو عِيسَى حَدِيثُ أَبِي هُرَيْرَةَ حَدِيثٌ حَسَنٌ صَحِيحٌ ‏.‏ وَالْعَمَلُ عَلَى هَذَا عِنْدَ أَهْلِ الْعِلْمِ كَرِهُوا الْغِشَّ وَقَالُوا الْغِشُّ حَرَامٌ ‏.‏

Grade: Sahih (Darussalam)
Reference : Jami` at-Tirmidhi 1315
In-book reference : Book 14, Hadith 118
English translation : Vol. 3, Book 12, Hadith 1315
https://sunnah.com/tirmidhi/14/118

Short answer is that cheating is not a trait of a Muslim and one should avoid cheating. If one has done that in the past then best thing is to ask Allah for forgiveness, try not to cheat again and give as much as you can in charity.
Now there are some other general question which I will try to answer below:

Say a friend took an exam before and he gives you advice about it? Is that cheating?

No its not cheating, don't overthink.

Students who took a class before sharing past exams or mateiral...is that cheating?

No its not cheating

Is looking up stuff during an online exam considered cheating? Some professors do not care and some do?

It depends, if it is an open book exam then its not cheating. And if its not an open book exam then yes it is cheating.

Am I supposed to confess to professor if I was involved with one of the steps above?

I don't think that you need to confess this to a professor. Ask Allah for forgiveness and try not to do this again. grades and degrees will remain in this world. In the grave, no one will ask what your GPA was or how many degrees did you get.

I also want to mention that our education system is designed in such a way that most of the classes don't prepare us for the job we may get in future. It really is waste of time and this education system only prepares people to act in a certain way - programming people to accept modern form of slavery. This education system does not encourage students to pursue their own talents, instead too much focus is put on grades. Most teachers don't care if students cheat or not, all they care about is their pay check. That's why we see that many teachers don't change their quizzes and exams. Students gets these quizzes and exams from their seniors and past the class without learning anything. Those who do get good grades, are not necessarily smart. They are only good to memorize things for a short time. Once they pass a class, often they tend to forget what they might have learned in school/college/universities.
I have changed career few times. Used to be a marine engineer and I can tell that I learned almost everything at work. None of my education was helpful at all when I first started my job. After moving to USA, I started working as Mechanical Engineer and once again I learned everything at job. School was good for nothing. You can look at the most successful people in the modern world and you will see that most of them were high school drop outs.
Anyways I have come to understand that home schooling is a must for Muslims in the West. We can teach our kids Quran, Sunnah and Islamic history to build their foundation and let the kids explore their own passion. Once a strong foundation is built, then they can pursue a degree if they want to or start a business at young age. This will save them from many haram things which are taught in the school system, help them to be more independent, more confident and they will always look at the world from Islamic point of view - not the view which modern school system want us to see the world with.

Anyways that's my personal opinion and not everyone has to agree with this opinion. Sorry for going a little off topic here.
Allah knows the best!
Ma'aSalaam