Replication priority
Yes, giving instance1 a higher priority will make the replicaset re-elect instance1 as the primary when it rejoins. See the docs on Adjust Priority for Replica Set Member and Replica Set Elections for more details:

Member Priority
After a replica set has a stable primary, the election algorithm will make a “best-effort” attempt to have the secondary with the highest priority available call an election. Member priority affects both the timing and the outcome of elections; secondaries with higher priority call elections relatively sooner than secondaries with lower priority, and are also more likely to win. However, a lower priority instance can be elected as primary for brief periods, even if a higher priority secondary is available. Replica set members continue to call elections until the highest priority member available becomes primary.