1) will the character be kept after OBT done?
2) will there be only 1 global server exist?
3) is there any instance beside regular quests?
4) where to farm/hunt rare/ultimate equipment?
1) Your character will continue over to the full game.
2) As of now, there is only one server for the time being
3) Yes, there are castle sieges for guilds, realm vs realm (faction battles) last man standing pvp, pvp, and a few instances you can find the objects for in game, but idk if you can interact with them just yet.
4)You could try the temple for a bit, and then the new area (the desert) will hold some more powerful equipment, but the best free equipment can be obtained through doing 5 daily quests 100 times, and then trading in your correlating tickets for prizes.
Hope that helps