How can I get the revision history and when edits were made?

You can see if there are archived copies at 

https://web.archive.org

You can of course ask IMDb when specific changes were made, though I don't know whether they would answer. They would almost certainly not tell you who made the edits.

Hi @kwtalkies -

Even if we could track down who sent a specific piece of data and when, it is our policy not to disclose contact details or any other information about our users and contributors.  So we are unable to provide the information.

Thanks for your understanding.