Is it ok if a new lower ball joint, out of the box, doesn't rotate freely like the one just removed?

You often can't move the stud by hand. It can take a lot of effort to move it. You won't be able to turn it either without a pliers, but that's not something you want to try to do. If it has a tapered stud, you don't want to scratch it. That taper is needed to hold it securely in the spindle.

It will turn easier when it wears a little. After you press it in, if you have to tap on the stud with a hammer to line it up with the hole in the spindle, that's perfectly normal.

Those splines hold the wheel bearing assembly together along with the axle nut that must be set to the specified torque, which is real high.

A somewhat common cause of a squeal, only when moving, on older Chryslers is the axle seal in the transmission. I suppose the same thing could happen to other car brands. If you spray behind the inner cv joint with Spray White Lube, the noise might go away for a day or two. That's a Chrysler product that I'm familiar with but other spray lubricants will likely work too. Spray White Lube is a lithium-based grease that is very runny at first. The juice runs into places and takes the grease with it, then the liquid evaporates and leaves the grease behind. One clue to help find the noise is it will still occur when the front end is jacked up off the ground and it's running in gear with no weight on the wheel bearing or suspension.