Can I still get married to a US citizen?

That is not a question about immigration law, but rather a question for the local clerk of court. You should be able to get married regardless of...

I am an Australian citizen currently in the US on E3 visa. Am I eligible to apply for a green card?

If you have an approved immigrant visa with a current priority date, you can file for a green card.

I have valid EAD ending 2014,STEM I-20, and OPT, but F1 is expired and i need to travel.Can i travel outside USA to renew my F1?

You should be able to renew the F1.

My L1 visa is valid from from July 1 2013. Can I reach in June on my existing B1/B2 visa provided I don't work till July?

They can often admit people 30 days before the start date on the work visa, so there is no need to arrive on a B visa and then you would have to...

H4. Otherwise she would need to file for a change of status after she gets here.

Applied 2007 ,denied Sept.2010 , reapplied and appealed right away and was approved Nov the same year.

It does not sound like you have any question about immigration law, you should direct this question elsewhere.

Is interfering with the delivery of mail a crime of moral turpitude for USA visa waiver immigration purposes?

I doubt it.

USC by Naturalization, filing I-130 for husband, will she need to give her Birth Certificate from abroad?

There is certainly no harm, and USCIS may request it.

Is there a way to expedite the immigration petition for my son as I have submitted a previous petition which was revoked?

Since your child was married before you became a US citizen, the visa became void. The second visa has been approved and will be available in the...

Is my German born husband a US citizen? After 52 yrs. does he still have to naturalize?

If his father was not married to his mother, he is not a derivative US citizen from the father. If his mother did not naturalize before he turned...