Thanks for your fast answer and help to solve my problem.
I have 3 shipment types: courier, personal collection and courier with COD option.
I have two payment types - bank transfer and COD.
I can set up COD option to be active only when COD shipment is selected, but I cant do that with bank transfer, so theres always radio button.
So if you select “regular” courier you have only option with bank transfer, but if you select COD courier you have to select also COD payment, because bank transfer is not disabled.
Thats why I tried lots of plugins and scripts with ability to conditionaly disable payment methods - and all failed, my conclusion is that its because I am using cornerstone pages to display delivery options, not woo default page?
I hope you understand now what is my problem.
And as for 2nd one, here is picture atttached:
Woocommerce options/advanced/features
Order data storage:
WordPress post storage (legacy)
And I need to check enable compatibility mode, because otherwise theres incompatibility issues error.
All plugins/wp/templates are up to date.