The first example is the best. You have to completely stop the flow of air for an instant by touching the ridge of your palate with the top of your tongue.
Yes, I have. I use it too many times. I prefer to speak some words which I feel I ca not pronounce well.
Yes, you are right. I dropped the t sound totally.
The previous ones were better. These sound like "light-uh-ning". You've introduced a vowel sound between the "t" and the "n".
No, it's terrible. The word "lightning" has only two syllables, not three.
I use you tube live people.
No. The problem is that you introduce a schwa sound in the middle. This has nothing to do with "lightning" having two "n" sounds. As I said, break it up into two sound units: "light" and "ning", and after practising saying those separately, try saying them one after the other.
It means the famous video site youtube.