Q2: The pinot-minor logs contains messages like the following:

2022-09-07T16:48:11.311344994Z76 START: CallbackHandler 0, INVOKE /pinot-quickstart/INSTANCES/Minion_pinot-minion-8.pinot-minion-headless.pinot-quickstart.svc.cluster.local_9514/MESSAGES listener: org.apache.helix.messaging.handling.HelixTaskExecutor@6c9febc5 type: CALLBACK
2022-09-07T16:48:11.311376624ZCallbackHandler 0 subscribing changes listener to path: /pinot-quickstart/INSTANCES/Minion_pinot-minion-8.pinot-minion-headless.pinot-quickstart.svc.cluster.local_9514/MESSAGES, callback type: CALLBACK, event types: [NodeChildrenChanged], listener: org.apache.helix.messaging.handling.HelixTaskExecutor@6c9febc5, watchChild: false
Info
2022-09-07T16:48:11.311654554ZCallbackHandler0, Subscribing to path: /pinot-quickstart/INSTANCES/Minion_pinot-minion-8.pinot-minion-headless.pinot-quickstart.svc.cluster.local_9514/MESSAGES took: 0
2022-09-07T16:48:11.311991754ZNo Messages to process
Info
2022-09-07T16:48:11.312021174Z76 END:INVOKE CallbackHandler 0, /pinot-quickstart/INSTANCES/Minion_pinot-minion-8.pinot-minion-headless.pinot-quickstart.svc.cluster.local_9514/MESSAGES listener: org.apache.helix.messaging.handling.HelixTaskExecutor@6c9febc5 type: CALLBACK Took: 0ms

Does that "No Messages to process" mean that it's not seeing any records in the uploaded file?

this is helix framework, meaning minion has no helix message to process