Hello! After freelance photographer completes commercial "situational" photo for me or photo where he uses models showing how to use product, must I ask him to sign a document claiming that all IP transfers and belongs solely to me from completion?

Run-on sentences do not work well in English.

you are not forced to make him do that.

if you want to ask him to sign, you can do that.

but such things are better to settle before doing the task.