I-140 duration + H-4 EAD process

[truth_seeker]

Dear Forum Experts,

Can you please help me with following questions:
For EB-2 category:
1. What is I-140 duration for approval, if normal processing is followed( i.e, not premium processing )?
2. How long does LC process take for approval( is it almost always <4 months)?
3. Can employee pay for premium I-140?
4. what is process for H-4 EAD & duration for approval?
5. What concerns of employers, make them push green card initiation dates, in general?

I appreciate your time & inputs. Approximations on duration is also much appreciated.

Thanks.