Hi Prashant,
It is not possible to prevent that changes in active version will overwrite the simulation version. Note "600841 - Features of a saved simulation version" describes this behavior:
"The system response is correct. A simulation version does not represent a copy of the planning situation when the save is made. A simulation version only contains the changes that were carried out during the planning. The following general points apply:
Changes to objects that were not changed in the simulation version are displayed in their current status in the simulation version.
Changes to objects that were also changed in the simulation version remain in their simulated status in the simulation version.
Confirmations, changes to the order quantity and the deletion of orders are exceptions to this rule. These changes also take effect in simulation versions if the affected objects were previously changed in a different way within the simulation version."
Regards,
Tiago