#2
Unless they specifically say its factory tuned to a certain tuning (Ibanez does it with some of their guitars) Theyre usually E-Standard, and 9-46 or 10-46 or 48.

Thats usually, its a fairly safe bet.
LTD MH-250NT (With EMG 81/85)
Ibanez RGT42FXQM
Bugera 6260
Seismic Audio 212
#3
ok because im to sure..its a mustaine signature and mustaine have signature ghs 10/52 and the guitar came ghs strings..i think ( because there was a ghs sticker on the headstock )