Upgraded Simphony 18.2 to 19.1 and R&A 8.5.1 to 9.1 . Steps as below
following below steps can be considered.
Refer Doc: R&A 9.1 installation doc
>>Page no 13
Uninstall Enterprise Back Office version 8.5.1,
To create a backup of the configurations, ...
SES VAT Implementation Guide lines for all the modules.