Upgrading Drupal

TLDR;

What risk would I run updating very old D7 sites to their most up to date D7 core and contrib code and module versions?

A little background,

Starting in 2011, I was a senior developer on a team that, over the course of 6 years, created and managed 20 or so enterprise-level D7 sites. Some of these were national level chains, some of them were major universities. Given that they had already invested so much in D7, less than a handful decided to go D8+. The rest decided to ride the D7 wave until EOL.

Is it possible to fix an incorrect upgrade process?

I did not update a D8 website correctly ... "The website encountered an unexpected error."
I moved all to my localhost. I get this message:

I've just tried updating my Drupal site from 8.9.16 to 9 following the document: https://www.drupal.org/docs/upgrading-drupal/upgrading-from-drupal-8-to-drupal-9-or-later]

Composer.json

I'm getting stuck on upgrading a Drupal site.

I did invoke

composer update --with-all-dependencies
drush updatedb

resulting in

the subject release is missing several .PHP files in the Vendor\Composer folder.  the Vendor\Autoload.PHP calls one of them (Vendor\autoload_real.PHP) and they aren't there.  I don't know any other method of notifying the community of this issue.

Thank you

Paul Cushing

someone could help me how to unblock the admin user and delete the flood table but I still can't enter

• El nombre de usuario admin no ha sido activado o está bloqueado.