nope it's not possible per se.

if you only need to share a common ID between datasets, you could as a workaround include a hidden field in the subsequent form(s) and preset it with the unique ID that you got from the first form.

1. first form collects input data.
2. second form(s) collect more data but also have a special hidden field (which will be preset with the unique ID from the first form)

on submission of first form,  the my-function.php logic needs to kick in to reroute randomly to one of eight pages (redirection overwrite)), each with a different second form on it

the redirection overwrite needs to parametrize the new UR, e.g.:

http://mysite/newpage?hiddenid=1234567

submitting the second form still is a separate process, but they are now connected through 'so to speak' a primary/foreign key method.

Now it is up to your SQL skills to craft proper SQL routines to collect all primary submissions and logically merge them with secondary submissions.