Is it possible to pair bluetooth speaker to iPad and Macbook air at the same time?

Yes, you can pair the speaker to more than one device. However, you can only connect one device to it at at time.

No.

It depends on the speaker. Check the documentation for the speaker you want to use.

To clarify my answer, you can pair it with as many devices as you want to but you can only use one device at a time which is what I assumed the question was implying.