H4 to H1B when H4 is pending approval

[manep]

I have worked on H1B from Nov-2006 to Nov-2009 and haven't left US for more than year.

I'm on H4 since Dec-2009 and it got expired on March 31st 2011 but H4 extension was applied on Dec 3rd 2010 and I haven't received approved H4 yet i.e it is still pending approval.

I just got job offer and company is ready to file H1B premium processing(since I won't be counted against annual cap and would be able to start job immediately) but my question is

1.If old H4 is expired and I haven't received new H4 yet.Is it advisable to apply for H1B?Should I wait for H4 approval?

2.What happens if H4 gets approved after H1B approval?

3.Would last action rule void my H1B?

Thanks