Kafka exclusive consumer retry behaviour

I need some understanding on the Kafka exclusive consumer retry behaviour for fixed back off.

Exclusive consumer is reading data from a topic having 6 partitions. All 6 partitions have data.
FixedBackOff(30000, 100) is applied to consumer for failure retry case.

1. Consumer read data from partition-0 and processing fails, retry with 30 secs interval starts happening. Will the consumer keeps on retrying this record from partition-0 or will the consumer can read data from partition-1 and process and holds data from partition-0 during next poll() ?
2. If it can hold data, then how does kafka ensures fixed backoff of 30 secs for every record in flight?