I did a 1031 years ago from a single family home to a duplex. I assume I can do a a 1031 from a duplex back to a single family, right?

If so, how long am I required to rent it out for a specific period of time before I can move into it? Thinking I could live in it for 2 out of years and then sell.

Yes you can do another 1031.

1031 allows exchanges for "like kind", meaning pretty much any piece of investment real estate can be exchanged for any other. However, there are some rules depending on the balance of any existing loan compared to future loans on the new property.

Basically, you have to avoid getting "Boot" (i.e. money) from the sale.

I swapped a four plex and two small SFHs into a 17-unit commercial property. So yeah, pretty flexible. I used a company that specialized in 1031 exchanges that was recommended by my Title Company. They made it effortless on my part. Just had to sign a few extra docs, and they acted as the intermediary to hold the funds until disbursal. Excellent experience, and only cost about $800, which is cheap on a deal of that size. Saved/deferred tens of thousands in taxes.

Sid is spot on about how boot definitions can look a bit twisted.

I once sold two places that were free and clear and wanted to buy at least two places on the upleg. So I sold $400,000 in real estate. The first place I bought was over $400,000 so I assumed I was good in completing the 1031. I placed $250,000 down on a $550,000 place. That left $150,00 for the second deal. Well the second and third deal I identified didn't occur. I got a tax bill on the $150,000. More over, I had to file a tax extension since that $150,000 in funds wasn't returned until the 180 days was up. I don't understand how that was boot to this day......but I do understand today that you use up 100% of that cash as quickly as possible in this market place.