What happens if black plays m9?

The move and the fight are fully explained in 9-dan Showdown (page 233). 211 was believed to be played either to gain time as he was in byoyomi, or to set up a resignation scene. There were no hallucinations. Black could have captured the white stones at the bottom, but he judged he'd be behind and so fought a big ko out of desperation. The whole lower fight was rated too hard for amateurs to read out anyway.

For the benefit of others, this was one of Go's most famous games ever: "The one with the three brilliancies" (Game 7 of his second match with Fujisawa. The game record above is incorrect. Fujisawa was still Kuranosuke, not Hosai.

or to set up a resignation scene.

This concept has always puzzled me.
When you feel you need to resign, why not just resign? Why do you need to 'set the scene'? Why make weak moves just to... what?
Can somebody explain?

For some Asians, it is an asthetic issue. The game needs to be complete. To just up and resign may make sense to you after you have counted, but the really good 'place to resign' is one that makes sense to anybody.
For someone like you or me, raised in a society that values individualism - maybe too much, some might say - it seems pointless. A game of go is just one person vs one person, and who cares if anybody else likes it. But to a person raised in a heavily group-oriented society - like the Japanese, for example - the game is not just two people, but two plus many observers. And those observers must be shown proper respect. The game must be obviously resignable to all observers.
To finish a game that only some people can understand implicitly separates the obeservers into to groups: those who can understand it, and those who can't. This is humiliating to those who can't. A proper Japanese gentleman whould never do that. He would ensure that a work of art is equally understandable by all.
The closest that we might find in our culture is if a museum had some space that was accessible only by stairs. The proper western gentleman would never have his artwork shown there where some people would not be able to see it.

i also look for a place to resign when i play.
if i know i am losing by few point and no other way to overcome that margin i choose more complicated perhaps overplaylike move.
either i resign or i get another chance to win.

how is this theory?

Hmm...
On a pro level - this assumes a hope for a cheapo - a silly mistake on the part of your opponent.
Do you think this is a plausible theory?

actually it is true.
nobody can read all variations so before resign they can verify their losing by playing moves that might not be optimal.
i am sure you play same way.

Hmm...
On a pro level - this assumes a hope for a cheapo - a silly mistake on the part of your opponent.
Do you think this is a plausible theory?

It is plausable. I heard it directly from a pro. Tadashi Sasaki 8P was giving a simul in LA last year. After I lost - despite a substantial handicap - in the post game review he noted that when I was behind late in the game I should have played way more aggressively. I pointed out the obvious problem - that he was too strong everywhere. He said that it didn't matter. He said do it anyway, that to do otherwise was 'walking step by step into your grave.'