Some short answers:
1) Most C4D users are generalists, with a particular speciality that they are best at. A big part of being professional is knowing your own strengths / weaknesses and being honest about them.
2) Showreels can be what you describe, where a person is an animator working with assets created by other people and comped by other people, but as I mentioned above, most C4D users generally do a lot more of the job than you'd find in bigger studios. If you're working at Pixar or Framestore then you might just be a Rigger, Animator or Modeller, but if you're working with C4D a lot then its much more likely that you're doing more of the roles yourself. I've worked at the Mill, Man Vs Machine, Nexus, Art and Graft and quite a few others and the C4D guys are nearly always generalists who are scary good at everything.
3) I'd say no, personally, if you're just starting out you should just do every tutorial you can get your hands on and then cut together a showreel of your own stuff. Senior artists who appraise your work can spot tutorial content a mile off, so if you have an personal projects you can do to differentiate yourself then that's a great selling point.
To get a junior job you just need to show passion, a level of technical ability, design chops (which hopefully you've got currently), and a willingness to put in work. It's not the sort of profession that cares too much about academic qualifications and how many courses you've done. You don't stop learning once you get a job, you learn more, faster. If I'm not scared about some aspect of a job (because I don't know how to do it) then I feel like I'm being lazy and not pushing myself enough.