You are always Welcome dear Bro.
Ok. I get it. But it's recommended to always use genuine and OEM recommended spark plugs. After market, or performance plugs can be harmful for the engine.
As per my limited knowledge; engine knocking has got nothing to do with Transmission or Catalytic Converter of the car. I don't understand, why mechanic is insisting on replacing Catalytic Converter, if it's clean and working absolutely Fine!
I would suggest to change the mechanic for mechanical related issues of your car. He is playing with your car and treating it as some toy.
For wrench icon and it's resetting, I think there is a Mitsubishi Ek Wagon Owners and Fans Club here. You can raise your issue there, and also search here on forums. It's resetting has been discussed here somewhere, some time ago.
And Yes, there is difference between jerking and knocking. Knocking is mostly related to engines and jerking is related to transmissions. Two things are getting intermixed and they are to be treated separately.