In this case the "as he likes" refers to the fact that internet learning is largely preference based. In other words, one is able to learn whatever one wants [whether it be learning a wide range of things for one's own enjoyment or simply learning that which they need to learn for a particular reason]. One is also able to chose when one studies and also how much of a focus to place on different sections within a subject. This is different from traditional, in-person classes which tend to follow a set syllabus... [The sentence is therefore referring to the vast freedom that internet learners have when choosing what to study and the control they have over when to study, simply as a result of having so many resources available to them on a 24 hour basis]. I hope this helps!

I think it means the student can study what he wants to, and in the way he/she wants.

In my opinion,it means:If you're interested it,it's much easier to grap the knowledge you wanted.