No, you cannot backup and restore 861 content on the 910 Repository without performing the Repository upgrade. You must perform a Repository upgrade between these 2 versions. Also the geographical location of the server is not a constraint to perform the repository upgrade and they can be in two different locations.
Repository backup and restore does not work across different Informatica versions. It has to be within same versions.
Follow the below steps to upgrade the Repository from 8.6 to 9.x
1. Take a binary backup of the 861 Repository that needs to be upgraded and Skip Logs while generating this Backup file
2. Prepare a new Schema for this repository so that it can be copied over or migrated preferably on the database instance where you your target domain metadata is residing
3. Create a new Repository Service in the Old Domain (861) and in 9.x domain with the name that you would like to have it on the new Domain (9.x) and do not create Repository content at this time
4. Enable the new Repository Service on the Old Domain
5. Restore Contents to this Repository Service (backup file taken in step 1) from the Repository Backup File
6. Once the Restore is complete, disable the Repository Service on the Old Domain (861)
7. Now enable this Repository Service on the new Domain (9.x). The Service will be started-up successfully and will display the below message.
The Repository version [xxx] is incompatible with version [yyy] of the product. The Repository version is 88 but the product version is 90. An upgrade may be required.
8. Now upgrade this Repository to the new version using the ‘Actions’ Menu.
9. Once the Repository has been upgraded, change the Operating Mode to ‘Normal’.