How can I apply for an extension on my re-entry permit outside the U.S.?

You must be inside the USA to apply for the re-entry permit. When the US embassies and consulates are open again, you can go in and apply for a Returning Residents'' Visa. Hopefully, the Immigration Service will issue some guidelines saying that if you cannot return to the USA, there will be no penalty.

You have to be in the US at the time you file for a re-entry permit and the application is only for a new permit. You cannot extend an existing one. If you stuck outside beyond one year, technically your permanent residence is terminated but in fact, this does not happen automatically and there has to be a determination. One option is the SB-1 returning resident but generally, they are restrictively adjudicated. So if you pursue that option, be ready to document extensively regarding the circumstances beyond your control that caused you to be out longer than expected.

You cannot apply for a reentry permit outside the United States. You should make your best efforts, and document them, to return to the United States before October. If not possible, then you will need to apply for an SB-1 returning resident immigrant visa at the U.S. embassy or consulate in your home country, once that office reopens.

Unfortunately, this is not an option. You must be in the U.S. to apply for a re-entry permit. You may re-enter the U.S. on the green card. If you have been gone more than a year you will need a letter from the consulate and perhaps an SB-1 immigrant visa.

You should t return to the U.S. before October 2020 or sooner if possible. If not you could be found to have abandoned your U.S. residency. You do not "visit" the U.S., as you are a returning resident. You must physically be within the U.S. to apply for a U.S. re-entry permit.

You cannot get a reentry permit or advance parole from outside of the U.S. At the most, you could try to return on your existing, expired reentry permit.