Will Putin sell more BUK systems to 3rd world despots now that he has proved it works?

It is a 40 year old system. A LOT of countries already have them. They are next to useless against any offensive modern aircraft and only really good at hitting slow large aircraft like a cargo plane (which normally do not fly in contested areas) or civilian jet liners (which should be smart enough not to fly over contested areas).

Ive got a musket I can sell you too if you like. It worked very well against Napoleon and is still pretty good at hitting large alow moving animals and people

Supply and Demand. It determines the market. So it's not out of the equation that putin will lose credibility but make more money but then again does Putin need to make money? The country is already rich in money and resources. Just not minds. That's why corruption is a national problem.

The SA-11 system is 1970's tech. As lana_sands said, lots of countries already have equivalent systems.

Was it Russia's BUK or the ones that the Ukraine inherited.

They are not exactly new tech. Most nations have similar systems already.

No, he won't.