Sunday,Wanted to change out platinum plugs of 2-4 year(found later that the old plug when out,gap is wider at 1 mm rather than the recommended 0.81 mm.otherwise old ngk platinum plugs BPR6EGP looked good) before emission test.
Loosened number 1 plug closest to radiator.However put NEW plug in at wrong angle and cross-threaded the top part of thread.Phoned mechanic who told me to tow car to his shop tomorrow.
Presevered for an hour,using OLD plug and some grease and managed to get Old plug back in.While threading plug in,initially hard to get it thread at correct angle,then after correct angle achieved,easy to tighten ie no grip then finally gripped tight.

Took the car to emission centre next day,PASSED test!!!!!!!!hooray.

Took it to mechanic,he said since it passed test,leave ALONE.He said I may have caused serious damage to the thread by persevereing and avoiding the tow.Now that it's tight and snug.Leave till next emission test in 2.5 years time if I havent traded-in the car (I did test a few months early).It sounded he only have a chaser and would refer his business to a machine-shop if necessary.

I've looked thru the archives regarding various rethreading tools,BACK-TAP(expensive$80),Time-sert(more expensive$350),IPD helicoil-type repair($32).

Should I get an IPD kit for $32 just in case I want to keep the car for more than 2.5 years.Any experience would be appreciated.

BTW,I cross-threaded the transmission pan plug hole too 10 years back,it was finger-tight only and cannot be wrenched tight.I added few drops of super-glue and let corrosion (Canadian salt)took care of keeping the transmission drain plug tight on the outside.Used exchange flush since then and inline ipd trans line filters(changed once)since.So far ,no leak at all.