No, they're not compatible. There were facelifts made to the vehicles between the two years.
Depends on many factors. Condition, mileage, engine size, options, location, and which Ford Truck Model. I will post a link to NADA where you can find out.
The 2006 Ford Focus has a 2.0 L base engine size.
The 2005 Ford Focus has a 2.0 L base engine size.
The 2001 Ford Explorer has a 4.0 L base engine size.
The 2013 Ford Mustang has a 3.7 L base engine size.
The 2012 Ford Taurus has a 3.5 L base engine size.
The 2007 Ford Taurus has a 3.0 L base engine size.
The 2014 Ford Expedition has a 5.4 L base engine size.
The 2009 Ford Flex has a 3.5 L base engine size.
The 2007 Ford Fusion has a 2.3 L base engine size.
The 2006 Ford Explorer has a 4.0 L base engine size.