pass password to a new person

Here is the official Adobe license transfer policy.

Added:  And since the term Upgrade is often used ambiguously, here is what you need to know:

If you purchase a new license, rather than upgrade your old software, you are permitted to transfer your old license—that is, as long as you did not purchase the original license with a volume licensing arrangement.

Hi peterb,

It seems that when you upgrade to a new version, you've already used up the option to pass it along, or selling it.

Here's the link to Elements 2021, you might want to check it out and have him decide if he wants to try it or not. It actually is a lot of fun.  Or he can also download the "trial" offer.

https://www.adobe.com/products/photoshop-elements.html

No. Not if you used the old serial number to upgrade; you own a single thing, 17-and-an-upgrade-to-19. Using or installing 19 is dependent on your continuing to own 17. If you hadn't upgraded, you could transfer or sell it, after completing some Adobe paperwork.