is it possible to destroy artifact creature (eg Iron Myr) with Vandalblast or does it specifically has to say "destroy target artifact creature"?
A card like Crush couldn't destroy an artifact creature. That's why Crush costs less than Shatter - because it's more restricted. Shatter can destroy artifacts whether they're creatures or not.
The Basic rulebook, read it! A lot of basic questions are answered there!
How to autocard :
Type [c]Black Lotus[/c] to get Black Lotus.
Type [c=Black Lotus]The Overpowered One[/c] to get The Overpowered One.