So if my low level character completes DG can I then play through skyrim main story mode as a vampire lord does anyone know please?

Also is it possible to max out vamp lord skill tree please?

Thanks

Yes.

yes and yes.

Thanks very much guys
DG is awesome!! Loving it!!

Where is best place to sell stuff & forge weapons once a vampire please?
Can I venture out in daylight?

Yep, vampire's dont take constant sun damage like in previous games. Check http://elderscrolls.wikia.com/wiki/Vampirism_(Skyrim)#Stages_of_Vampirism_and_their_effects out for more information per stage.

Also, note that if you have the Dawnguard expansion, people no longer fear you even if you're at stage 4. They only freak out and attack you if you transform into a vampire lord.

Awesome!! Thanks Louise

Forgot to ask!! If I am in my vampire lord form in daylight what's the downsides if any please?
And what's the exact sunup/sundown times please? Do these stay the same please?

I don't know the answer to your first question, but the time in which vampires are affected are 5am to 7pm.

Downside is that your health, magika, and stamina don't regenerate and I'm not going to spoil it but there is a quest item that can help with this. I believe it's 7:00 am to 7:00 pm. Mabye 8 to 8. Not sure exactly.

Yeah i finished the MQ as the VL just yesterday and it was quite easy (Skuldafn was Cake) but you still need the dragonrend shout which means that will have to do certain fights in human form (At least half the fight)

Thanks guys
So to be @ my best I gotta roll @ night!!