It almost sounds as if the expression レベルが高い to describe a 大学 infers a little at all three, but in this expression it likely leans in meaning towards 2. and 3.
Usually it is the schools with the highest prestige that are all 1. the most expensive, 2. offer the highest grade of instruction, and also 3. have the toughest exams for admittance. I think it is a modern short-hand to describe an institution which actually meets all three of these criteria.
In this case, then, it depends on the position of the speaker, to identify which of the three the meaning leans toward when the speaker says 簡単に合格できない.
If the speaker is already a student there
This probably leans towards the high grade or difficulty of class topics or pacing.
If the speaker is a prospective student
This might lean towards speaking about the difficulty of the entrance exams.