So what exactly is that iron meat parasite that can infect humans and different structures? We know military keep it on the moon and military during level 4 start to develop vacine for it. I would say that they find it very quick or already have developed earlier and need to mass production it. Is iron meat created by humans as bio weapon or it is alien orgin found somewhere by humans?

I'd bet on the extraterrestrial origin. When the game starts, even before the outbreak on the Moon, screen of the computer terminal could be seen. And there is an alert message in russian on that screen: "Марс потерян!" -- "Mars is lost!"
Therefore it looks like yet another big corporation dug something ancient out of the red planet and tried to put it to military use. Usual things: absolute weapon or absolute soldier. And, as usual, everything gone highwire,
The meat itself looks like specifically engineered either nanites or sort of proto-life. Snice it almost indistinctably integrates with both live matter and machinery. And obviously demonstrates some tratis of Campbells's "Thing". Or rather Carpenter's interpretation.

https://youtu.be/waeU5-aw2V4?si=D1dfBL8eunx0h7NI
Retroware post story explanation on YouTube. Now we know for sure that Meat is not rogue military bio weapon, it is actually small part of bigger being that slip through moon teleport gate and was discovered by Yuri Markov, he keep it secret in his moon lab, it grows, break free and consume Yuri. Also somewhere during game Meat send escape pod from Moon to Mars.