Well, the news from you is ominous

I've contacted the old mechanic to come & take a look at it. Towing it to his workshop seems to be the only option I have.
I will lay your last 3 posts before him to assess the situation. A denter(bodywork expert with no engine experience) gave me some faint hope saying that it might be an issue of water having seeped on the piston heads & rusted them out & some valve there is spoilt. Thus requiring some polishing(on the lathe) of piston heads & replacing the valves. His logic being that ever since the car was started after a 2 year gap it was misfiring. This will be the 4th opinion to give to the old mechanic.
The 5th opinion of a mechanic who heard the engine sound through the video says "connecting rod bearings which have worn out due to lack of engine oil which has increased the clearance and causing the knocking sound when accelerated"
This whole present situation is difficult to absorb. A car that was driven in with no engine issues for bodywork has reached this stage.
Will fill you in with the latest...