1. Will multi classing be a thing?
No word yet, but I can't see them leaving it out. It's too easy to add. There is some classic multi-classes existing the subclass system already.
2. Are dlcs planned after release?
No word yet. Someone mentioned they were not big on DLCs in previous titles, but I know they've added content after release before.
3. Is leveling gonna work like normal dnd?
Technically we don't know, but 5e levels quicker than traditional D&D. It's very quick to level 3, a little slower to level 5. Then average from level 5 to level 14. And finally, fast again after level 14.
4.Please tell me your adding as many monsters as you can like even ancient dragons and other crazy monsters.
No word yet.
5.will the world have plenty of legendary items to find that we can use?
Treasure will be hand-placed unlike Divinity, there's tons to draw from, I assume they will.
6. is the game gonna have a solid main story or will it be more about exploring all the quests in the world?
More main story, I'm sure.