2. Signature software can prevent your mobile phone from being poisoned, but this is of little significance. Personally, it doesn't matter at all, because all useful software is virus-free. It's a big deal, Gejigeka.
3. Of course, you can't install without signing, if it is software that needs signing.
Most of them won't. If they will, it's a big deal.
5. ".Sister" and ". Sisx "is the difference between s60v2 and S60v3. SIS is the second edition, but both sis and SIXX can be used in the third edition.
Because the software of 5800 is the fifth edition, many softwares are useless. But everyday software is enough. However, there is no special edition software for the fifth edition of S60 of qQ, so you can only use the java universal edition, but you can use the latest third edition of QQ with the virtual keyboard, which feels ok.