Replace rear wheel bearings

Front or rear? What are you trying to do / how are you trying to get this apart?

The bearing is replaced as an assembly by removing five bolts. You can buy just the bearing but you still have to unbolt the entire hub assembly, then use special tools to pull the hub out of the bearing, then the bearing out of the housing. It's much faster and easier to just replace the assembly.

Nope. Just a splined shaft that might be rusted in. Obviously, be sure the nut has been removed from the cv joint. You can try pounding on the end of the joint with a hammer, but you run the risk of damaging the threads. If you have a new nut, as many of them are one-time-use-nuts, put the old one on backward a few threads, then pound on that.

You can also use a bearing puller that bolts to three of the wheel studs, and has a center bolt that is screwed in to push on the joint. It isn't common to have to resort to that.