I own these products and they work good for me. One thing to point out is that the character one does not make/nor animate entities. It makes already animated entities game ready. Not to take away from his sales, but, this can be done without the tools, but the tools take a lot less time than any other method I have tried leaving you more time for making your game. They also make adjusting your settings a snap especially when making various versions (static, dynamic, different texture, etc.). I have also had great customer service from Bullshock. I have not email him in a while, but I think he's still around.
Here is the link to his sales site:
http://www.sequoiagames.com/fpsc-toolbox
EDIT: sorry I didn't answer your question, Entities, weapons, and characters are not so much dependent on what version your running. Features are. So, for example, a crate made in version 1.1 will work with the new 1.19 BETA. If a custom character like the TF 341 soldier, use a feature like the custom variable that was not implemented till 1.18 (I think), then it won't work in 1.15, 1.16. etc. Hope that helps. You can always go forward, but sometimes not back.