1) You can run workflows and pipelines from Java with the Apache Hop dependencies (you'll need more than one). Here's some more information:

https://hop.apache.org/dev-manual/latest/sdk/hop-sdk.html

2) PDI 5 and 7 have nothing to do with Apache Hop, and Hop won't change any behavior in old PDI versions.

Hop 2.10 is built with Java 17, we keep up with newer Java versions as much as we can.

Feel free to reach out if you need more in depth help.