I suggest you try some of the tutorials, this will answer most of your questions, anyway, here is a short note.
1. chemical potential
Yes, there is an analysis object
2. P DOS(PROJECT DOS)
Use denisty of states object
3. Bloch state
Yes
4. how many no. of electrode on device configuration
2
5. we can calculated non linear i-v char. of any diode (p-n , tunnel diode)
yes
6.diff. b/w bottom and top approach or atk depend on which approach.
I dont understand this question
7.you have any manual of diode configuration like as - P-N DIODE.
No, not yet
8.is it possible to include new molecule in vnl database
You can import molecules directly into VNL, we take different formats, use import from file in the add menu to see the supported formats