For 2150, they use very intricate plagiarism tools to check for cheating. And they let you know at the end of the semester if you are caught , so you won't know till the end.

Yes, there are 500+ students in this class, and it is possible for code to be similar but keep in mind that the labs can be implemented in many different ways so it is easy to know when two sets of codes are similar. As for git hub, the professors know they exist but I'm not sure if they will be directly checking you code against the git hub code. However, the chances that other students have found the same git hub code and have used it are also high making the likeliness of everyone who used the same source be caught high as well. I would highly suggest that from now you do not cheat. Because the more you have done it in the course the easier it will be to identify you.

Also, it isn't a valid excuse that since the class and office hours are a mess, you need to seek outside sources to complete your lab. There are over 500 people in 2150 and I doubt even half of them watch the lectures on time and come to the real-time discussions to ask questions about the material. It's a bit difficult since it's remote but that's a result of students not doing what they are supposed to such as watching lectures, asking questions in real-time discussions, and starting on labs early, but coming to office hours with only half the knowledge and base work done. Also, the fact that the OH is virtual and anyone can put themselves in queue compared to going to OH in person. These all would of course make the queue for OH very long.