No. Hoppers meant for the cyclone feed will only fit the cyclone feed.
Most systems will fit adjustable feednecks. The only major size differences are .50 caliber hoppers, and the tippmann cyclone hoppers, which have very large feedholes.
No. They are all Tippmann clones without the Tippmann durability.
No, all paintball hoppers have a standard neck size.
The majority of hoppers have a standard neck, and most feednecks (where they attach) are adjustable. The only large difference in sizing are the Tippmann A5 hoppers, which are many inches across, to feed the cyclone feed, and .50 hoppers, which cannot fit standard paintballs.
Not at all compared to actual paintball guns.
Tippmann is the best brand too get. Spyder is another good brand that isn't as good of a gun but Tippmann's are a bit more expensive but there is really no difficulty with Tippmanns at all. Invert mini is the most expensive gun around these days ( 500$ ) or the Bob Long guns.
sorry i do not know
Yes, all brand paintball guns use a tank or other source of pressure.
All paintball guns, excluding high end guns, have a .685 bored barrel.
Regular .68 caliber paintballs, all standard guns do. Also there is no "m16 paintball gun" , only guns that look like it.
Tippmann and azodin all carry good reliable entry level markers.
No. The tippmann sl-74 I and sl-74II are threaded for sl-74. The tippmann pro-carbine is pro-carbine threaded. The Tippmann 98 is 2 different threads, they changed half way through production. An older barrel may not work on a newer gun because of tighter tolerances in the older stuff, but you can buy adapters if you happen to get into a jam like this. (Mostly you don't have to worry about this unless you get EXTREMELY unlucky) Tippmann a-5's are threaded for a tippmann a-5 adapter witch then screws into the gun. Tippmann x-7's are the same thread as a-5's. Hope this helps!