While these components are open source and you are free to test them and install them in Cloudera Kafka, they are not supported and have not been tested by Cloudera's dev team.
1 & 2) Starting with version 2.0.0, KafkaStreams was included with CDK Powered By Apache Kafka, however, it is not supported. Spark Streaming is the tried and tested technology for processing streams of data, and Cloudera has around hundred customers using Spark Streaming in production settings. In addition, with Spark Streaming, Cloudera's customers are able to benefit from the superior Spark ecosystem and libraries and machine learning support.
3) Schema Registry is currently not supported. As it is open source, users have the option to install separately in an unsupported manner or building your own lightweight alternative as per:
4) You may install and test KSQL as it is open source. It is not tested & not supported by Cloudera. While functionally different, Spark Streaming may provide a solution for your use case.
Hope these answer your questions!