Please don’t post the same topic in different forums thank you.
And now for your questions.
Many programs has their source code published as well as code examples, all you have to do is to search the forums, and if you don’t find something you want to know about than ask for it.
There is no API, therefor you’ll have to do things by inspecting behavior. Most (if not all) of the programs just use Windows API to send and retrive data from paltalk.
Tools you can use are: ResHacker Winspector and PEBrowse Professional, those are the utilities I use (as I rather not pay for anything 
.)