Trying to interfere with peer review is always a bad call.
If you don’t thoroughly document your code, no one but you will have a clear understanding of what it’s supposed to do.
It’s a good thing to keep your original data.
Proprietary data makes it much harder for other scientists to do quality control on your work.
Folks may judge you by your behavior, not just your data.
These are just some of the bulleted points. There are enough quotes and exposition on each and much more in Dr. Free-Ride’s post. Go take a look at it.