You are always welcome. Всегда пожалуйста!
You are quite right!
- Можно ЗАДАТЬ (perfective) еще несколько вопросОВ?
( the student here intends to ask his questions at one time, e.g. during the lecture he is attending, not over a period of time.
Therefore, his asking questions is viewed as a singe action that will be completed upon the professor's permission.)
- Пожалуйста, я люблю, когда студенты ЗАДАЮТ (imperfective) умные вопросы.
(Here the professor refers not to a single, specific one-time action, but rather to his habit of gladly answering the clever questions every time they are asked... Besides, characteristic, habitual and repetitive actions are expressed by the verb in its present tense-form, and present in Russian is imperfective only.)
Good job