alrighty I actually know this stuff B)
spider queen will be the first boss, however it won’t be a dungeon boss. this means it’ll arrive before the mushroom king dungeon, but the date depends on the work the developers have done so far
the level cap will most likely be raised at the start of beta (early summer) which will be in about 6 months. to compensate for max levels, there will be extra things to work towards such as leaderboards (not sure if it’ll come anytime soon though)
now, you’ve actually gotten the raids and dungeon bits completely wrong. in berezaa’s first vesteria dev stream, he stated that raids will be 50 players all fighting together, with an extremely high level cap (his example was level 70) this means that the raids won’t be appearing until vesteria is free to play.
dungeons, on the other hand, are 6 players of a certain level requirement entering a dungeon to defeat a boss. there would be 1 life only, time limits, puzzles, and more during the dungeon. this means that there will probably be more than one room in dungeons
as for berezaa’s example, he stated something along the lines of: there’s a dungeon in the mushroom forest, and a guard by the entrance. he goes “hey! the mushroom king is here! go kill it!” and you go “ok lol.” however, the guard replies with “but you can’t go alone! come back with a full party of level 20s or higher or you’ll die!” so you do that, enter the dungeon, and get murdered.
berezaa also stated that the dungeon will be hard, so going with a full party of 20s is almost guaranteed to fail