Hello @pringadi_synopsys
The ability to create custom fields has existed in the v2 REST API for a very long time:
https://docs.atlassian.com/software/jira/docs/api/REST/8.15.1/#api/2/field-createCustomField
You can’t create screens via the v2 REST API, only change them and add fields to them:
https://docs.atlassian.com/software/jira/docs/api/REST/8.15.1/#api/2/screens
The topic of not being able to create screens via the v2 REST API has been extensively discussed on other threads.
There is this existing thread from Atlassian on the topic of the progress of updating the REST API for managing screens, but relates to Jira Cloud and the v3 REST API.