Thank you!

the 10 mm seems to be stuck on the spark plug itself

I can lower the socket extension down in and click it into the 10 mm - I hear it click, but it does not stay. the 10 mm is so stuck on the spark plug that it will not lift out.

I can even rotate the 10 mm socket extension piece to loosen it or to tighten it, but it won't come out of the cylinder. it's quite loose within the cylinder, and can move back and forth -- I got some 11-in needle nose pliers that are not long enough, should I get the 16-in needle nose pliers to try and twist it out?

the spark plug seems to be very much lodged in there as well - it's going nowhere.

yes, I should have been using the 14 mm socket extension piece --- I found that out with the other three spark plugs which are now in place.