I'm not sure about all your requirements. We automate getting the latest versions from PerForce and building our app with batch files and other tools.
1. My batch file for getting the latest versions is really simple:
My guess is that you could probably use some of the other command line options to get specific changelists. How much have you studied the documentation for the command line interface?
p4 sync //MAIN/MyProj-Version1/...
2. VC6 also has a command line interface that is fairly easy to use. You can also generate a make file that can be run from the command line or a batch file. You can adjust the make file as necessary to build the right projects. If you VC6 workspace is set up properly, it should handle the dependencies.
3. Again you can do this with a batch file or using a scripting language like Perl or vbScript. You just have to learn the language.
You might also want to look for something like Ant or NAnt, which helps bring together all these different steps like make does. Maybe a combination of NAnt and some scripting will get what you want done, but you'll have to do work yourself learning these tools and setting them up. I actually had to do something very similar to this almost ten years ago when I started my first job. It wasn't that fun but I learned some new tools and got it running.