How can an EB-5 investor apply for a re-entry permit if the conditional green card has expired?

They will ordinarily approve for up to the period of the extension, that is about 18 months.

There is a specific process at the U.S. consulate abroad depending on the consulate so please contact/email the U.S. consulate to request the process.

Yes, you can apply.

If you are able to obtain a reentry permit, it likely will be valid only for one year or for no longer than the remaining time on your extension notice, whichever is less.

You are eligible for a re-entry permit in this situation.

If you have filed the I-829, you will be able to apply for a re-entry permit because your conditional residency is extended while the I-829 petition remains pending. However, the expiration date of your re-entry permit will be the expiration date of that 18-month extension period. If you have been out of the 18-month extension period and there is an I-551 stamp on your passport, the expiration date of your re-entry permit will be the end date of the I-551 stamp.

You can travel on your expired green card and extension notice. You only need a reentry permit if you will be outside the U.S. for more than a year at a time.