Undo has been available in the Alt Menu of GBoard for a while. Long press on an editable text field then select Undo in the popup alternative menu (sometimes you need to scroll over or tap the 3 dots to see the full menu choices)

How is it fair to send an 18 year old to war but not let him vote?

Where do you live where you can enlist at age 18 but don’t have the right to vote‽ Not in the USA…

I’d vote for him

Have you considered listing your services on Dumpling? https://www.dumpling.us/personal-delivery-tools/pdt-signup

Useless if the door swings shut by default, likely from poor horizontal alignment.