Why do all Tor hidden services websites are static with poor graphic and simple coding? Does the Tor network support all coding languages?
First of all the Tor network itself doesn't support any coding languages it just moves data back and forth.
The performance on Tor and especially on hidden services is not the best, therefore hidden service operators may use low resolution images/graphics as they are easier to distribute over Tor.
I'm not sure what websites make use of .onion domains and if scripting would make any sense for those, but the simpler something is the less room for failure there is.
To answer the question, yes, one could create a dynamic website behind a hidden service.
Yes, of course you can use dynamic languages. Almost all forums, markets, wikis etc, on hidden services use them (often PHP, I've noticed).
Operators of hidden sites might be wary of using server-side scripts, because they can be attacked anonymously, and it's difficult to block individual attackers.
On a clearnet site, attackers can be blocked and rate-limited by source IP address (or ranges, AS numbers, country code, etc). On Tor hidden services, there's nothing anyone can do.
So someone can attack your hidden service all day and you can't block them without affecting legitimate users.