The only way to reset the ECU is at the dealer.
No there is no way to tell if the new O2's are working correctly.

I just re-read your original post, you need to replace your plug wires too.
You may still be getting a random mis-fire, even with new spark plugs if your wires are bad it will have the same symptoms. And if you are dumping to much fuel into the cats it can give you O2 codes.

 

Well, I was going to replace the wires when I replaced all spark plugs, but didn't figure out how to get access to the distributor cap as it appeared at the end back of the engine which I found no way to get there. So I only did the spark plugs and O2 sensors and was thinking to wait till having those codes cleared and to change the wire.

Can you pls let me know how I can do the wires? Thanks!

 

You dont have a distribitor cap, you have coil packs. Yes they are at the back of the engine.
As far as replacing the plug wires goes, it is a real pain on DII's. I have never done it but I have heard that it is a 6 hour job.
When you replace them you remove one and then replace it, then move onto the next one.

 

step 1 id usually say would be to use factory sensors, nothing is made to the exact specs as oem parts, and with tolarences as low as they are something thats not perfect is essentially wrong. that said, i think youre looking at a short, check your wires going to your sensors on the rh side by the drive shaft, seen those connectors come off their brackets and rub the shaft. now, that said, you should be seeing alot more codes, if those wires rub, and your heater wires short out, itll blow fuse 2, which control most of your sensors, so im back to the aftermarket sensors. get it checked out, but dont just keep driving it like itll fix itself, it wont, youre overcorrecting your fuelling as it is, you will burn out your cats iff you keep going