Can we edit baan standard script ???
How to change in baan standard script ???
Does the change in the script modify the original functionality ???

If you own sources then,
Can we edit baan standard script ???
yes
How to change in baan standard script ???
change code
Does the change in the script modify the original functionality ???
depends on your coding
Andreas

Small Advice:
Try to avoid doing any changes in the Standard Script.
Copy the scripts and then do necessary changes.

As an alternative you can also encapsulate the original script, using it as a dll and change the functionality of the session or dll without changing the actual, original source.

Such utilities such as Rush (on this site), RMCGen, or Qkey also help with that.

For report scripts you don't need to have sources. you should be able to edit it.