not the typical cat to go on this gen ody, its usually bank 1 due to vcm oil fouling / damage.
unless you were continually driving the vehicle with misfiring cylinders on bank 2, or the cat was replaced with an inferior aftermarket one due to a collision in the front.

 

Before going down a rabbit hole, look under car and confirm CAT is there. Need to ask with rash of thefts.

 

According to this DIY replacing catalytic converter (bank 2) on 2005 Odyssey?, the front bank 2 is near the radiator. Did they change the location in the 2012 model?

 

O2 sensors do go bad.
YES, it's different. See this thread O2 Sensor downstream location
"Bank 1 sensor 2 (O2 sensor) is located in the rear, closest to firewall.
Bank 2 sensor 2 (O2 sensor) is located in the front, behind the radiator. "

 

roughly 600...

a walker cat from rockauto is 365 + tax and delivery charges, gaskets.
1.5-2 hours labour charges unless you diy.

try a bottle of cataclean first...