Can I find my alien permanent resident number online if I don't have the card

There isn't an accessible data base online. A person may make a FOIA request. You might try an infopass.

Can I change my name again?

A person seeking to change their name without a document doing so may stop the process and restart.

I'm applying the I-130 for my son who is 24 year old and single. Do I have to send along the I-864?

The I-864 is not required at this time for the I-130 of an adult son. It will be requested when an immigrant visa is available in several years.

Very difficult to overcome a denial at the border. A consultation with an immigration attorney may help.

Yes, passport photos are required for the filing of I-485 and related forms.

What is the procedure to be followed now?

You have not stated the basis of 'rejection'.

My green card expires in 8 months but I’m moving states within the next 3 months. Should I file now or wait till after the move?

Marriage to a US citizen can be relevant for 'when' you file. A person filing for naturalization may file 90 days before the qualifying years....

I apply i jun for n400 . i didnt receive anything yet .

You should call the 1800 375 5283 or make an infopass and inquire.

Can I visit my husband in the US on an existing B1/B2 visa? My husband is currently awaiting his citizenship.

It is possible a person married to a permanent resident may visit the US on B1/B2. It is also possible to be denied admission.

Can the same employer file a new H1B petition for me with the same title while my last year petition is on appeal?

An employer may file an H extension for someone within their I-94 validity. A new filing during a pending appeal requires more information.