So, here is progress.
I didn't have to wait for next day.
After few sim hours later, I checked family tree of that newspaper deliverer, the game sims to have killed that teenager newspaper deliverer and hired 3 child newspaper deliverer (I have set pool of 3 for newspaper deliverer in register).

Wait, you tried that? I warned that you do it at your own risk. You might get a deformed monster or some other error. You have assigned this victim of an experiment to the service using Register for your home? Did he come to the porch with a newspaper? What is the result? Can you give some amount o...

Well I just tried suggestion from Sara and the teenager became newspaper deliverer. Is this bug then? I find that surprising. Are they actually showing up every sim day to deliver the newspapers without errors? I don't know I just done it so, I have to wait until next day to see if he/she shows up ...

There actually is no solution to be had here without reprogramming the game as said and it's not the fault of Register. Teens and older cannot be newspaper deliverers. They can pick up the part time job in the Journalism career and work 5-7am every morning in a rabbithole coordinating newspaper del...

Oh, ok.
Thanks for reply.
I will try that.

P.S.:
I checked the option in the Newspaper Delivery Service Sim.
It showed I could change the number of pools (Number of Sim that can be Newspaper Deliverer)

P.S2:
Even I got solution I can try, I will still consider more suggestions or ideas about this.

Well, I wanted teenagers also do newspaper deliverer.
Is there way for them to have newspaper delivery job?

I tried to change newspaper deliverer age and went to register settings.
I click Valid Ages, it does nothing.
Is this suppose to happen?

Oh, ok, thanks for reply. Sorry, I tried spoiler feature, but it doesn't work. Looking at the Medical Careers of Other Sims Series, I think I would also wish there are other Sims Games' Medical Career Levels. Sims 1 1) Medical Technician 2) Paramedic 3) Nurse 4) Intern 5) Resident 6) GP (General Pra...

I have a question/questions about EA's Medical Career.
When I look at the Career Track Level, it doesn't say anything about Doctor/Physician.
Which one among those are Doctor/Physician?

The world lot can count as a "room," so technically they can be "same place" as other sims coming at going elsewhere across the world at that time. Again, I don't know of any way to stop that from happening and am not sure what the logic behind it is other than EA wants our sims to be friendly (or ...