ishuaji is easy but to change the su into english is hard. so i advise u use mgyun, do read pevious post on how to. as for unroot, u can use the unroot option in supersu, tested by one of us and proven to be ok.

Regardless any rooting tools, all are the same = ROOT the phone. You can just pick any to your liking. For I, I used the mygun method as it's the easiest, which I can too unroot the phone using the mygun. Unrooting can also be done using the SuperSU apps.

Regarding the warranty issue, once you root, technically you void your warranty. But there are cases reported that the service center (Samsung) still permit rooted phone to claim warranty. However, best not take this for granted, this exceptional cases might be due to the overlook of the technicians, who knows?

And for the 3rd question, well technically, you have altered (root) your phone, even you unrooted it, the warranty is still voided. Traces of rooting your phone might have stored in your phone somewhere. Nevertheless, unroot your phone again might make it harder for the technician to trace back the alteration you made, not that it's impossible. And, the best way to cover your "tracks" is to flash back your phone to the stock, using the "Acatel One Touch Upgrade"
Extras:
1. For those who cannot flash your phone via the "Acatel One Touch Upgrade", getting the "wrong model number" error, it might be due to getting a somewhat different "Glory 2S"... I have compared 3 Glory 2S obtained from two digi centers, two can be reflash to stock using the tool, while one get the "wrong model number" error. The differences between the 3 is, two which can b reflash have "TenTen" hologram sticks to the battery and the phone, and a "Sirim" stickers sticks at the phone, another does not. Can those who can't reflash check their phone and report back?

2. The one without the hologram and Sirim sticker cannot be unlocked permanently, even though I can obtain the Sim Me Lock code from Digi...