1: South East Asia or Europe West
2: 100 to 250 ms
3: Yes you can shift to any server you like to play and that wont affect or slow down your Level progress or XP...But Each match will be counted for the Server you played on. i.e 100 matches on SEA, 50 Matches on EW Server.
4: Pakistani player base quite good compared to other MOBAs.
5:You will get some Experience points(XP will depend on your K/D/A ratio+other factors) for each match you play and you can play MMR/Ranked Matches after you reach Level 13 and it goes on...But you wont get any XP if you are in Low priority.
Enjoy!