1:  It's possible both to retrieve any ticket from jira and map it to whatever you want on SM9 side utilizing the Jira REST API.  Tickets from Jira to SM9 can be handled either as WebHooks in Jira sending information to SM9 - I would suggest going through a custom transaction table in SM9 so you have full control of what's happening or you can use a get function to retrieve. 
Update back to Jira is a bit more complex due to a quite rigid structure in how updates are handled, but yes it's possible.  Biggest issue is uploading attachments as Jira doesn't support base64Encoding OutOfBox so you have to upload with multipart/form-data and adding binary data to that doesn't work (at least for me) in SM9.72 JavaScript.  We have used 'curl' in between as workaround for that function.
Remember - there are not two similar Jira systems out there so your field mapping need to be flexibel - here is an example of an update transaction:
{"update":{"comment":[{"add":{"body":"Status Changed from: Updated By Customer to: Solved"}}],"customfield_11714":[{"set":"SD33612226"}]},"fields":{"customfield_11719":"Closed - On Hold","customfield_11687":"3","customfield_16100":"11053839403","customfield_16007":"CI4062857","customfield_14204":{"id":"16100"},"customfield_16009":"Application","customfield_16011":"N/A","customfield_15600":{"id":"16617"},"customfield_12407":"Personal Internet Banking / FS\n"}}
Here is a link to the Jira documentation as well:  https://developer.atlassian.com/server/jira/platform/rest-apis/

1:  It's possible both to retrieve any ticket from jira and map it to whatever you want on SM9 side utilizing the Jira REST API.  Tickets from Jira to SM9 can be handled either as WebHooks in Jira sending information to SM9 - I would suggest going through a custom transaction table in SM9 so you have full control of what's happening or you can use a get function to retrieve. 
Update back to Jira is a bit more complex due to a quite rigid structure in how updates are handled, but yes it's possible.  Biggest issue is uploading attachments as Jira doesn't support base64Encoding OutOfBox so you have to upload with multipart/form-data and adding binary data to that doesn't work (at least for me) in SM9.72 JavaScript.  We have used 'curl' in between as workaround for that function.
Remember - there are not two similar Jira systems out there so your field mapping need to be flexibel - here is an example of an update transaction:
{"update":{"comment":[{"add":{"body":"Status Changed from: Updated By Customer to: Solved"}}],"customfield_11714":[{"set":"SD33612226"}]},"fields":{"customfield_11719":"Closed - On Hold","customfield_11687":"3","customfield_16100":"11053839403","customfield_16007":"CI4062857","customfield_14204":{"id":"16100"},"customfield_16009":"Application","customfield_16011":"N/A","customfield_15600":{"id":"16617"},"customfield_12407":"Personal Internet Banking / FS\n"}}
Here is a link to the Jira documentation as well:  https://developer.atlassian.com/server/jira/platform/rest-apis/

Hi Jan.

Thank you for your suggestion.

Do you know the sample script to create a page Confluence from SM via REST API?

I can do it by Postman successfully, but when put code to SL of SM it can't combine

Thanks.

Neo.