Let me help you with this.
The Intel® Xeon E5-2620v2 can run without ECC memory but in case of needed it supports the ECC memory modules as well.
You can check this information at the following link:
In regards to the over clocking question, at this point is possible to over clock the unlocked processors (the ones that end with letter K) and I am afraid to say that this processor is a locked processor.
Thank you Kevin_intel for the very helpful answer!
You are welcome!