You have much to learn but hopefully we can help.
1. An M4 vs. an M16 is an M16 has nearly double the length in barrel.
2. The first link brings me to a G&G M4 Carbine and the second brings me to a G36.
3. Thats an EOTech replica, those are the way to go. Just the sight itself is a red dot with no magification, but you can buy a 3x-4x magnifier that is mounted in front of it.
4. Thats an ACOG, some are just red dot others are 4x magnification.
The M4 has MANY variants such as Carbine, CQB and so on. The G&G products are the same enternally but are different in appearance such as stocks rails and lengths.
Last edited by Muffin; April 8th, 2009 at 19:44..