Is Chi's Sweet Home 3D a sequel or a reboot? Is "Chi's Sweet Home 3D" an anime sequel of "Chi's New Address" or is it just a reboot?
Chi's Sweet home is the Prequel to Chi's New address.

Chi's sweet home aired from Mar 31, 2008 till Sep 25, 2008. 

Around the same time the following year Chi's new address aired from Mar 30, 2009 till Sep 24, 2009 

Source: Chis Sweet Home &amp;  Chis Sweet Home Atarashii Ouchi.