OrderStatus and OrderShipmentStatus can be extended, but they are not meta classes, you also need Commerce 13.0 at least https://world.episerver.com/blogs/Quan-Mai/Dates/2019/2/new-feature-in-commerce-13-extendable-orderstatus-and-ordershipmentstatus/
Not quite sure about your first question.
I have a case to update purchase order data with payment details, orders status and cart data.
I'm able to update status of purchase and payment but i'm unable to update cart. That means I would like to change/replace the order details data wth new cart which was updated.
And One more doubt is , can we extend OrderStatus and PaymentStatus meta classes?
Please help me is there any way to do the same?