1. Dry firing causes unnecessary wear on internals and may lead to breakage.
2. Indifferent. The company has a spotted past but I will let their future actions influence my opinion.
3. There are lots of reputable online retailers. Since you neglected to list your location in your profile I cannot recommend any walk in retail stores.
4.Internally they should all be essentially identical internal wise. At least all the armalite variations and the scar at least, they all run off of a version 2 style mechbox. All you really need to decide is how you want your airsoft gun to look.
G&G isnt a terrible brand but the money can definitely be invested in something better.
"Its only a little bit on fire"