There is an error Error: Unknown field state in domain [["state","in",["final"]]]

Add <field name="state" invisible="1"> in the view where you are using above code you describe.

Thanks for help.. I got it now.. but I'm wondering can i do this in .xml, because if I use this in .py I need to put readonly=False, states={'final':[('readonly',True)]}, in all of my fields and it is to many.. Technically when my state becomes final the whole form should be in readonly.. Thanks

You can do it in xml but here also you need to add attrs like: attrs="{'readonly':[('state','=','final')]}" in all fields you want to make readonly.