His question is Changes in Order Header (Order Status = ENTERED) , in terms of changing
Bill - To
Ship-To etc .
Please note that Changes in Order Header are not depend on how you create the Sales Order ( Copy /Import or Manual Entry) , it's all depend on your Processing Constraints ( Seeded + custom), customization , defaulting Rules,personalization etc.
For Additonal Info on Processing Constarinst , please refer my post Processing Constrainst in OM
Here I will discuss only the PC.
e.g - System will not allow you to change Order Type if Lines already exists in the system , but it let you change Price List , Bill - To , Ship -To etc.
So wheneven you plan to make a chnage in your Sales Order or want to build any customization based on Changes on the Sales Order , you need to visit your Processing Constraints Rule.
Below are 2 Processing Constarints Rule.
Below seeded PC will not allow you to change Order Type if
Order Type is Gapless , OR
Status = Booked , OR
Lines exists in Order.
Similarly below PC will not allow you to change Order Header if Invoice activity is complete.
Also System will not allow you to disable Seeded Constarinst and sometime disabling some of the seeded constraint is not good for business.
You need to review all the PC and check what is possible and what not.
Hope that helps