Don't know if this is what you mean but you could use for example $orderby=Name asc to alter the order.
Only way to do this, as far as I know, is to change the attribute sequence on the entity itself, and then re-export the service feed.
Yes, the order of the properties is described in the metadata, so it's always the same.
Why do you want to do that?
It seems that OData has added support for Column Sequence order, any idea when it will be made available in Mendix :)