Can I apply for H4 EAD now?

Apply for the EAD if you want employment authorization. Speculation as to what may or may not be is just speculation

Will I be able to come back to US, if I go to cruise with unstamped H1B visa on passport?

If you have a valid visa and evidence of valid status and a valid passport - yes to all

There is no active move to repeal the Cuban adjustment Act. In the event it is repealed it will not affect pas =t adjustments.

I751 error

Wait a couple of weeks for receipt as it often takes 3 to 5 weeks.

Can I continue attending classes if my EAD card has expired?

if you have valid status that permits attendance at school.

Can I travel from the United States to South America with my Perminant resident card?

Yes you may return to the US with permanent resident card and valid passport. For entry to countries you want to visit, check each countries rules...

What are reasons for cancellation on green card through marriage interview without no reasoning?

Unlilely anyting to do do with Trump and overstay - more likely not and is due to staff taking time off or something not complete in background...

Que puedo hacer si me dicen que me tengo que ir en 2 semanas

Esta no es una cuestión de inmigración. Póngase en contacto con un abogado que maneje asuntos de arrendatario.

Is this normal?

Contact CIS and inquire as to when you will be scheduled. Use customer service or info pass

When can i apply citizenship?

The day you were approved for CR. According to you was 6/28/12. You may apply 90 days prior to 6/28/2017 if the date you provided is correct.