Canadian citizen (with no criminal record) applying for a green card, and sponsoring husband with a criminal record.

You might want to go back to the attorney and ask for clarification. Based on your post, it doesn't appear there is a waiver available, but we...

B2 visa

We can't give you a firm Yes or No. But definitely carry evidence you are leaving, e.g. return plane ticket, evidence of sufficient funds for...

How can I check for the validity of my green card, whether or not it is still valid

If you lost your card you can find out how to replace it here http://www.uscis.gov/green-card/after-green-card-granted/replace-green-card.

F2A Beneficiary- Should I still maintain the F1 status?

We don't know your case so we can't assess risk. You have to decide how "safe" you want to be. Based on your post, Its likely low risk at this...

Query on 'Out of country'

If you are asking about the one year you must spend outside the US to restart the H and L clock then it's from the day you left the US.

Do i need to change my Last name 1st before i can petition my husband?or do i need to change my marital status?

You can petition your husband without changing your name or marital status. You will evidence your relationship with the marriage certificate.

Can I marry my girlfriend (US citizen) after entering the US on a tourist/ visa waiver program. Or do I need a financee visa?

The key is intent, if you find yourself swept up in romance and get married in the US while on visa waiver and then you leave to process the...

H4 candidate is in USA while H1 candidate is in home country for short visit and visa stamping.

As long as she is processing the visa and intends to return to work as H1B you are in status. If an unusual delay if months occurs then you want...

ETA 9089 is PERM. Processing times are posted here http://icert.doleta.gov/#fragment-2, it takes 60 days after filing unless the case is audited. ...

You can work on your H-1B until the change of status to H4 is approved.