For the date you are using dashes in the parameter name where you are supposed to use underscores. So created-at-min should be created_at_min. That means https://my-store.myshopify.com/admin/orders.json?created_at_min=2014-09-01 should work to get all open orders since 2014-09-01.
To combine filters you separate them with an ampersand. Thus, https://my-store.myshopify.com/admin/orders.json?created_at_min=2014-09-01&status=any will give you all and any orders created since 2014-09-01.