What are the different forms of access that have been provided to the basic level of knowledge? One could cite libraries, classrooms, laboratories, professors as sources of knowledge at a university, and studying at a university affords access to all of them. What is “single source access”?

I don’t think there’s a hard rule mitigating for or against “by,” I would tend to lean in favor of it, however. “Studying in the university” casts, to me, the notion of a specific time or moment of study, whereas “By studying…” conveys the general idea of study that, in turn, provided access to the desired knowledge.

How can I gain knowledge in university though study?

You can’t use the “the” in the front of access. Second, as you are talking about the event in the past, it will be appropriate to change the present tense “desire” to the past tense “desired”.

While the -ing is used in the verb “study”, it is insignificant when you start in the verb “studie”. Why is “by” followed by “-ing”? Should you use the -ing form and not just the -ing form as you are going

to be studying? Besides, you can use the -ing form to give areason. So this clause means “as I was studying in the university”/”because I did not have any time at university”.

On the other hand, when you tell the way you achieve something, you use by + the -ing form.