Upgrading Drupal

When I am using updater I get this Notice:

Notice: Undefined variable: conf_path in require() (line 730 of /home/users/orlcz/simulators.cz/web/sites/default/settings.php). Přejít k hlavnímu obsahu
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Hi guys,
I've a BIG problem with my website.
I'm trying to update my website because it has more problems and the control panel suggest me to update database .
When I go to update.php page, I press on continue button and I read the follow messages:

3 PENDING UPDATE

system module

7080 - Convert the 'format' column in {date_format_locale} to case sensitive archer.

block module

7009 - Increase {block}.title length to 255 characters.

node module

I feel at wits' end with this one. This is a custom multisite (2 sites) installation that I'm tasked with maintaining.

The system is running 7.22 and I manually updated the core (7.43) and modules on the server and cleared cache. When running /thesite.org/update.php it says there are no updates to apply. Running cron still shows that 7.22 core (and all old modules) are still in effect and in need of updating, even though all files are updated on the server. I have seen a good few posts on this and tried *all* of the solutions I could find from these threads:

Hello,

I just updated my site from 8.0.6 to 8.1.0 without any errors. My sites report status had not issues.

My site looks fine when I'm not logged in (i'm the admin). When I log in I lose all styles. It's only text, images and hyperlinks. I have a vanilla LAMP server. My drupal site is all out-of box except I enabled the forum, but never created a forum. I did some minor color changes, icon and main site image changes.

Bartik 8.1.0 (default theme)
Seven 8.1.0 (admin theme)

I'm approaching week 10 of trying to get a relatively simple D6 site to upgrade to D8. The migrate tools, either through drush or through the web UI appear to get us nowhere - content is never moved, users are moved, but the information seems incorrect and it appears permissions are changed - as well as user1 from the new site being overwritten with user1 from the old site, making admin access somewhat wonkey.

I'm wondering if a traditional in-place upgrade is even an option. It seems that it can't be as bad, let alone worse, than using the upgrade tools...

Hi

We have multiple sites running on one physical server.
We are still working with Drupal 7 on them.

But we have been receiving messages to update the version.

I was wondering: If I update one of those Drupal versions, will the remaining sites stay with the old version?
I would not want to jeopardise their status, so I thought I'd check here before I do anything :)