Unsupervised sports (including weight training/bodybuilding) can lead to injuries which can affect growth. That said, supervised weight training does not stunt growth (Malina, 2006). In fact, even high intensity workouts do not negatively affect growth if done under proper supervision (Ratel, 2011).
You're asking a lot of questions and they aren't as specific as they probably should be for a site like this. Let me just cut to the chase, and then try to justify my answers.
Can anyone reasonably expect to obtain a physique like Arnold without drugs? No
Can anyone reasonably expect to obtain a physique like Arnold with drugs? No
Can tall, skinny guys ...
Possibly real, but not "10 (or even 8) 'ab muscles'"
The appearance of compartmentalized 'ab muscles' is due to an anatomical structure called the abdominal linea alba.
It is common for there to be three 'tendinous intersections' (on each side) which create the classic 'six-pack' appearance -- however, studies of cadavers indicate that, due to genetic ...
The 4 c body composition model which is considered as a gold standard in measuring body composition changes indicated that there were reductions of percent body fat (%BF) from 9.1 to 5.0% when measuring body composition changes in 3 elite male bodybuilders during preparation for competition.
Per Withers RT et.al. in 1997, "The 4 compartment body composition ...
It's completely commonplace to increase muscle mass while reducing body fat.
It's trivial to find 1000s of articles and papers on this, random examples https://health.usnews.com/wellness/fitness/articles/can-you-gain-muscle-while-losing-weight , https://www.healthline.com/nutrition/body-recomposition#how-it-works , https://www.verywellfit.com/mistakes-to-...
The solution of the apparent contradiction may be in the scales of time:
At any point in time, you can either slim down (catabolic, during excercise) or build muscle (anabolic, during rest after excercise), but
on a more coarse time scale where excercise and rest phases are "at the same time" both can happen "together".
See e.g. the ...
There is nothing inherently damaging about weight training that would stunt the growth of a young person.
The basis of the claim was from the idea that the still active/open growth plates at the end of bones would be damaged by injury, preventing further growth. Indeed, injuries to the growth plates can stunt growth.
Dr. Rob Raponi, a naturopathic ...
Yes. That's the normal state for beginners with more than enough body fat and no physical excercise.
Yes, different people get different tips on how to improve, it totally depends on your current physical state.
This even stands true even for older people, e.g. this study comes to the conclusion:
These results support the hypothesis that older persons who ...
Can skinny guys get as big as Arnold the bodybuilder without performance enhancing drugs?
No. No one can. Humans appear to have a maximum potential for muscle mass (warning: includes advertisement for ebook).
There is a very relevant article A Review of Issues of Dietary Protein
Intake in Humans International Journal of Sport Nutrition and Exercise Metabolism, 2006, vol. 16, pages 129-152.
The rate at which the intestines absorb amino acids depends upon the protein source, and, according to table 2, this varies from a low of 1.3 grams per hour for egg protein to ...