How to reinstall TOS for your TNAS?

[angelor]

For example with 1169 i had a lot problem with Jellyfin that did not start after upgrade; and after contact the support, try and try, i had to unistall and install it againg and reconfigure all my client devices..... with 1140 it was fine. It was very frustrating

So i would like to have the steps to "downgrade" TOS7 just in case a problem occurs after manual/automatic update of TOS7 version.
I red the viewtopic.php?t=423 but the TOS installation package it always related to the last version....

how can i install a specific TOS7 version ?
Thanks in advance