I am unsure if English is your first language or not, but the question could be worded better.
I'll try though!
Construct Classic is completely free, and you can make commercial products with it. You can make your own engines and everything.
Construct 2 requires a license, either for standard use (recommended for hobbyists) or business/commercial (for a small company).
As far as using other third party engines, if someone has made an engine here and shares it, nothing is stopping you from using it, since it's all just built from the event system anyhow. However, I am not sure if that's what you mean.