Is it obligatory to seek forgiveness from the university for entering a student-specific event without permission, knowing that the person authorized to grant forgiveness is unknown, and without benefiting from any food or drink, merely staying for two hours? And what about parking in a company's private parking lot without their knowledge, due to the absence of signs and not knowing whom to ask for forgiveness?

Regarding the first question: nothing is incumbent upon you towards the university as long as you have not damaged any of their property or benefited from any of their services, and have not consumed any food or drink. The custom is to be lenient in such matters. If you wish to seek forgiveness, it should be from the university administration.

Regarding the second question: absolution is achieved by seeking permission from those who own the benefit of those parking spaces (the company management). It is likely that they will forgive you, as this is usually overlooked.