No. No license is required.
A rail interface system or a mount on the top
Usually not. But you must cock it between each shot.
8.4v 1500 mAh
I don't think so but check just in case
Air Soft guns. Yes
In general, no, However, the requirement for ANY kind of license for ANYTHING depends on where you live- and you did not share that with us.
in general 180 $ is the minimum for a reliable rifle.
soft clean cloth
No they are not illegal.
Try oiling of the gearbox.
No you don't as long as the buyer is over 18 yrs old it is all legal and ok
Contact the maker to see if it is possible and what it will cost.