Can you help me understand some of the estate tax laws regarding property?

I know currently $5 million is exempt from estate taxes, and I think the tax rate is currently 35%.

I am trying learn about estate tax regarding real property and family farms. I was in a discussion about estate taxes and one of the people brought up the movie Secretariat, which I have not seen, and that the family lost the farm because of taxes. Here are my specific questions:

Is it estate taxes that create impossible taxation for families as they inherit property, or is it local property taxes or both? If you know specifically about what happened with the Secretariat situation that would help me too, but I would like a general answer about the laws and how they impact families, and if the laws have changed over time.

Are primary residences treated differently than business, secondary residences, and open land?

Is real property taxed at the same rate as cash?