I have seen youTube video'* in which they claim that engine misfire in the cylinder was caused by incorrect gap. Can this happen...Does the gap change with time if it is set properly at start? If true, I was thinking of checking gap every so often (maybe 30-40K)

The gap would not change from normal usage. Also, on aluminum heads, the less often the plugs are removed and installed the better.

If this is the Sonic with 36,660.9 miles (59,000 kilometers) on it, then it should have factory plugs installed and they should be gapped properly.

A mis-gapped plug will cause a misfire. If gapped properly before install they are fine until erosion of the tip increases the gap. Which is usually at the end of its lifespan or improper combustion causes them to fail early.

Today'* high end platinum plugs last about 100K before needing replacement.

I've seen plugs with near zero center electrode. Burnt down to the porcelain.

New fangled ceramic air gap sparkplug. Top dollar right there!

They were old cars with state of the art plugs.

Made by Tesla

I'm betting a 36,660.9 mile (59,000km) Sonic doesn't have improperly-gapped spark plugs. I think the source of this thread is the slight vibration complaint in this other thread, and my bet from the description is that this is typical GDI 4-banger in a non-premium car that is in gear and has the AC on at idle on a hot day just doing its job. I'm not sure because I haven't evaluated in person, but this is my belief based on what I know so far. Inline 4-cylinder engines are known for a slight vibration like this at idle if the manufacturer didn't go to a bunch of extra effort to remove it.

Regarding my "non-premium" comment: If this were a high-dollar Mercedes or similar, they would have bothered to tune this vibration out of it. This is a compact "world car" that doesn't have nearly as much cushion in the budget to tune such things completely out. I'm not saying anything about the owner nor their choice of vehicle.

Based on this post in this thread, this car has quite a while before it reaches the 97,500mi/156,000km spark plug replacement interval, so the plugs are likely not remotely worn out.

I just updated the other thread with a post referencing one of countless articles on this issue.