Streaming Replication - SLAVE )Read - Write to Read Only Scenarios

Hi Experts,

I converted a postgres 12.1 SLAVE to read-write in case of abort/crash of MASTER(It was setup with Streaming Replication) using pg_ctl promote

But with pg_ctl promote there is impact on the Master always.

When I bring up the MASTER and ran "select pg_is_in_recovery()" on SLAVE, it returned false.

postgres=# select pg_is_in_recovery();
pg_is_in_recovery
-------------------
f

Is there a better way to handle this and what are the options to rollback and go back to Original state?