Problems with update gitlab 8.4 -> 10.1

Context. There is a gitlab-ce version 8.4.1 with a couple of old projects. It was planned to start new projects, so I want to update the system so that it will work the next couple of years.
What I did (Ubuntu 16.04): apt-get dist-upgrade && gitlab-ctl reconfigure . Yes, I’m fearless (the project code was cloned along with all the branches!). Gitlab was updated to 10.1, but it did not start.

Opened gitlab-ctl tail , saw something about postgresql :

connection to database failed: could not connect to server: No such file or directory
   Is the server running locally and accepting
   connections on Unix domain socket "/var/opt/gitlab/postgresql/.s.PGSQL.50432"?

– without thinking for a long time, I saved the folder with data and removed postgresql. Installed a new one (was 9.2, gitlab 10 works since 9.6). Everything is cool, but it certainly did not start with old data, I had to think about pg_upgrade . I did something like that (ie downloaded old binaries and put near on the server to make pg_upgrade), fixed some more bugs of gitlab-ctl tail, which easily googling (something about the old config was there). And … received :

NoMethodError: undefined method `default_group_visibility 'for #
Did you mean? default_group_visibility =
               default_project_visibility
               default_project_visibility?
               default_project_visibility =

The problem was found recently, and probably it will not be the first to solve it. I wanted to roll back , but remembered that I had Ubuntu 14 before upgrade, and gitlab 8.4.1 can not be installed on the 16th. And it became lazy.
What should I do : read official upgrade manuals .
But it’s too late to drink Borjomi. How it all ended. As it is written in the comments on the link , I demolished everything, installed clean gitlab 10.1 and using the instructions of Raveren here – uploaded the projects. The whole history is preserved.