sale or gift of Dorico

I know this has been discussed before and I am aware of the Steinberg re-sale info https://www.steinberg.net/en/support/knowledgebase_new/resale_wizard_software/registered/soft_elicenser/multiple_licenses.html regarding this, but I have a couple of specific questions:

If you want to sell a product you’ve received as download (for example, via Download Access Code or by purchasing online), you need to provide the buyer with a backup of the installation file on CD, DVD or, for example, on a USB flash drive.
In case you don’t have a CD, DVD or a downloaded installer, please contact our support team before offering the product for sale.

I don’t have the installer any more - couldn’t the new owner download the trial version of Dorico and I send him the license on the USB eLicenser for him to complete the transaction by registering the trial version?
if not, how can I get the complete installer again? I assume just copying the program won’t work for an installation, correct?)

my version is for Windows, what if the buyer is using a Mac?

Anyone - even people without any valid license - can download from the Steinberg website the Steinberg Download Assistant and by means of this Assistant can download the full installer of Dorico (and also other Steinberg products). So it basically just comes down to transferring the license to the purchasing party.

And the license does not care about Mac or Windows, it will equally work on both.

Thanks. So, to make sure I understand this correctly - if the person I want to sell/give it to has downloaded Dorico and if I then send/give him a USB eLicenser with the license on it, he can then register and use it? Can he use a soft eLicenser on his computer to run the program, or will he always have to use the USB dongle with the license?

He will always have to use the USB-eLicenser.

…because once a Soft-license is on a USB-eLicenser it can’t be moved back to the Soft-eLicenser on your harddrive. But you can transfer licenses from one USB-eLicenser to another USB-eLicenser.