1st time drone user & I bought an Air 3S.
Can i use a structure, like a house, as a point of intrest & if so where can i find a tutorial on how to do that? I'm having troubles even turning on active track.

Look at a few youtube tutorials. Get Higher than any obstacles.hit poi and draw a square around a stationarty objest thne move tyour right sticl dlowly to the right and keep it level. Stop if you need to.

Yes, it's really easy. "Draw" a rectangle with your finger, you get instructions you can skip and then either have the drone circle automatically or just have the camera locked on the object and move the drone up, left/right, forward/backwards as you like.

The short answer is - yes.
Have a look at this video to help you.
There are numerous others on YT.

Yeah you will get the hang of it.
Not very difficult once you know how.