Guild Wars 2

Recently bought HoT and i need to understand few things.
1. Leveling masteries needs XP, after a while i figured it out. But where is the most recommended to get lots of XP?
2. About Dragon’s Domain, how do i get there? I see the roads, but i those are blocked by a wall, how and when those walls are cleared so you can continue?
3. I see 2 lvl 80 maps upper from Verdant Brink, can you access them? And how?

1. Doing the map Meta Events earns the most xp for me, specifically Octovine (in Auric) and Dragon’s Stand.

2. You need to run the Dragon’s Stand meta event to complete map exploration there. The event starts every 2 hours and requires a map-wide effort of players. Once the 2 hour window starts, use the LFG tool to taxi into a map that is organized for the meta.

3. The one on the left is a Guild Hall (entered via a guild) and the one on the right is a Raid which can be entered by a Raid Squad (you can enter solo if you have a commander tag).