Q.1. recovery.conf file merged into postgresql.conf #
Postgres Pro 11 and below used a configuration file named recovery.conf to manage replicas and standbys. Support for this file was removed in Postgres Pro 12. See the release notes for PostgreSQL 12 for details on this change.
On Postgres Pro 12 and above, archive recovery, streaming replication, and PITR are configured using normal server configuration parameters. These are set in postgresql.conf or via ALTER SYSTEM like any other parameter.
The server will not start if a recovery.conf exists.
Postgres Pro 15 and below had a setting promote_trigger_file, or trigger_file before 12. Use pg_ctl promote or call pg_promote() to promote a standby instead.
The standby_mode setting has been removed. A standby.signal file in the data directory is used instead. See Standby Server Operation for details.