At 18 months he had mostly replaced spinning wheels with lining things up, but he still loved to watch things spin and gear toys were a big favorite. ...
At 2 I stopped keeping records of this stuff because we became more concerned about his social deficits and less excited about his learning. We put all of his puzzles and educational toys away for many months as part of his "therapy" and stopped teaching him things that 2 year olds "should not know". We are just now deciding to ignore all of that and appreciate him for who he is and nurture his natural talents. I wish I had never listened to them.
The spinning is (as you know) a classic sign of autism. My DS used to love spinning pot lids on the kitchen floor.
Re: the academic interests: I see no reason to suppress them, but I do see a real reason to actively teach play skills. This is pretty crucial for kindergarten. You might look at "Floortime" (Stanley Greenspan's books)-- they suggest using what the child is interested in to bridge over to new skills. We used to do pretend play about the planets, and then space travel, when DS wasn't interested in pretend play about people. Use the interests to foster real dialogue skills (not monologuing, but two-way conversational exchange). This both helps your DS stay happy and increases his skills.
I wouldn't spend any time on "math facts" or other skills of that kind at this age-- but spend time building the skills he will need to interact with other kids and with teachers.
DeeDee
