i would like to know how to return to the code after packaging the project

Since no one has replied:
I have researched this topic several times across the years. Once your vb code is compiled it will be in a lower level language. Even if you could open the exe file (and I have yet to find a way to do this), you will likely not be able to make sense out of it unless you can read machine code for the system you are using.
Back in the DOS years we used to share/collect vb programs. They could be edited, etc because they are Intrepreted, not compiled. This is no longer the case.
The threads I have researched today all seem to end with "can't do it".
If you find a way, please share.

I think it is necessary to know how to return to the code page because sometimes we need to repair the programme recived by customer - So if that can't be done, I think the solution is keeping a copy of not compiled project to do the repairs....... if you find other way ,please share

Yes, an exe file can be opened in NotePad, but what is there is nothing like vb code.
That, plus what you say about saving the VB Project would seem to be the answer to your question. It may not be the answer you were hoping for, but please mark this as solved if your question has been answered.