2002 V70 2.4L - I have code 2110 "Front Heater O2 Sensor Preheating Signal" and slight pinging/knocking (sounds like a deisel car) when engine is under load. Q1: Will replacing the O2 sensor fix this? Q2: Will an after marked O2 sensor be OK (cheaper, I assume)?

 

I would replace the sensor with a Bosch only. These cars do not like cheap O2 senors.
Then I would run a good injector cleaner through the system and see from there.
I like the Techron for the injector cleaner. You just dump it into the fuel tank and go.