Node Failover information

I would like to know some insights of failover scenarios. when i do graceful failover and stopped in mid time. Again i started failover of node. i readded the same node with delta recovery. but i got error as “deltaRecoveryNotPossible”:1.
just would like to know when failover started, is it continuous or all replicas becomes active once failover completes.
also what happens when i stop failover in the mid.