feat: add version downgrade for live-migration FAQ

Signed-off-by: Harkishen-Singh <harkishensingh@hotmail.com>

This commit adds a FAQ question that helps users to downgrade
TimescaleDB version on their target database to match with the
source database. This is useful when the source database (MST) does not
have the TimescaleDB version that the target database is installed
with.

migrate/live-migration/live-migration-faq.md

@@ -19,6 +19,41 @@ the migration. The logs of these processes can be helpful for troubleshooting
 unexpected behavior. You can find these logs in the `<volume_mount>/logs` directory.
 
 
+## Source database does not have the latest TimescaleDB version
+
+Live migration requires the TimescaleDB version in the source database to be the same as
+that in the target database (Timescale Cloud). However, in certain instances, the TimescaleDB
+version installed in the target database may differ from that available in the source
+database, such as in the case of Managed Service for TimescaleDB. In such scenarios,
+instead of upgrading the source database, an alternative approach is to downgrade the
+TimescaleDB version in the target database to align it with the version available in
+the source database.
+
+
+This can be achieved by first uninstalling the TimescaleDB extension from the
+target database using the following command:
+
+```sql
+DROP EXTENSION timescaledb;
+```
+
+Then, reinstall TimescaleDB extension with the desired version:
+
+```sql
+CREATE EXTENSION timescaledb VERSION '<version>';
+```
+
+<Highlight type="note">
+You might need to reconnect `psql` with the `-X` flag to prevent reading the startup file.
+</Highlight>
+
+To determine which TimescaleDB versions are available on Timescale Cloud and can
+be used for the downgrade, execute the following query:
+
+```sql
+SELECT version FROM pg_available_extension_versions WHERE name = 'timescaledb' ORDER BY 1 DESC;
+```
+
 ## Why does live migration log "no tuple identifier" warning?
 
 Live migration logs a warning `WARNING: no tuple identifier for UPDATE in table`