100-300
Depends on if you are talking about a real one or a semi-auto copy.
Yes
WASR is one.
Depends on which make, and what version. Typically $400-$600.
yes it's safety lever has a SEMI AUTO option.
100-1000 USD
Yes. You can own both NFA registered transferrable full auto firearms, and semi auto clones.
Depends. The original, Soviet, military AK47 is capable of full auto fire- pull trigger, shoots until you release trigger. However, the majority of the civilian versions of the AK47 are semi auto- 1 pull, 1 shot.
The M14 was never factory made as a semi-auto.
In semi-auto they can be found for as low as $350, but the full-auto cost much more around $13,000 after you get your class III licence to own one.
The SKB M-7900 is a pump shotgun not a semi-auto.
Go to a gun store, pay for it, fill out the 4473, and receive it once you've completed your background check.