Backup and restore Outlook ost data files

When the computer was first set by me about a 10 years ago (win 8.1), I installed a small SSD (120G) and moved C:\users (SSD) to D:\Users (HDD).
Outlook (office 2010) was installed only to import the 2 UOL (ISP) emails accounts from Win XP Outlook Express. At that occasion it was remained as Pop3 server and two pst files (for two UOL accounts) where created.
All data from D: were backed up on another internal drive (F:) every time the computer was idle.
On 2016 I upgraded Win8.1 to Win 10 and it remained on the SSD and D:\Users on the HDD.

About 3 years ago the Win 10 failed during an update and a technician was called to fix the computer.
The technician simply formatted the SSD, installed Win 10 and made links to the data that was on D:
He installed Office 2016 and set the server to use IMAP. All emails, address book etc that were in use on the two UOL accounts before the fail were not used and were lost.
About a year ago a GMail was created aside of the other two others UOL accounts (that were already planed to be replaced due to ISP issues).

What was done to fix all this mess.
- My friend decided Clean install Win 10 and to close the two UOL IMAPI subscriptions but would like to keep the emails (sent and received).
- On Outlook 2016 I created two data pst archives and moved all emails from the live UOL accounts (OST) to the PST archive. There was no address book on it.
- After creating a drive image on the backup drive, the SSD was formatted and Win 10 21h2 was installed. During setup I moved C:\Users to D:\Users using Kari tutorial.
- All data that were already on D: was then moved to D:\Users\Gessia folders
- Office 2019 was installed and IMAP GMail was created. The related ost file was created and updated from the GMail server. The two UOL pst files created from the two UOL accounts were set as data files.
I found the two UOL pst files on the backup drive and they were updated the day windows failed. This two UOL pst were inserted as two data files and they have thousands of emails and contained hundreds of contacts on the address book.

On Outlook 2010 the IMAP files are saved on a PST file that can be backed up and restored.
Newer Outlooks save IMAP files on a OST file that can be backed up BUT CAN'T be restored so they are useless.
As *.ost files cant be loaded into a new Outlook installation, you have to save Contacts, Calendar, Tasks and Notes to a PST file to separate emails (on the *.ost) and contacts, Calendar, Tasks and Notes (on the *.pst)
On the new computer you create the account, it will create the ost file (downloading emails from the server) and then you import the pst file with Contacts, Calendar, Tasks and Notes.
Shame on you M$.