I think it's a rendering of Tocharians, also known as Yuezhi or Yueh-chih. If you'd like to find some information on them, search for those names (especially the latter two).
No. The only actual examples of iron cuirasses found are those mentioned, but we do have Hellenistic representations of iron cuirasses from southern Italy on terracotta figurines.2.As far as I know,iron cuirass of Hellenistic period were discovered in Epirus,Macedonia,and the region once occupied by the Sarmatians.I wonder if armors of this kind were discovered in places such as Sicily, Asia Minor,Peloponnesus,and so on,which were more "civilized'~~
No. As discussed in that thread linked above, it's fairly clear that that man is wearing a long-sleeved tunic in the Persian style, which was fashionable among Graeco-Macedonian cavalrymen from Alexander's day until around Pyrrhus' death.3.Is there any archaeological evidence of the combination of cuirass and mail,as shown by the armor worn by the Hetairoi in the EB?
No, and IIRC the EB team has stated that they will change it.4.Mail veil was said to be of Iberian origin,and was used by the Seleucids.Is thereany evidence to support this?