ScriptRunner for Jira CLOUD post function email notification to stakeholder

[Khairul Basher]

We are implementing JSM cloud and using ScriptRunner for Jira CLOUD for post function as we have few custom fields. and we want to hide issue number in notification email. Customer can use 3 different channels and all stakeholder will be notify by e-mail through post function, I have few challenges:

1. In notification email SUBJECT, Hyperlink (<a href="{{createdIssue.url}}">{{custom field}}</a>) on Custom field is not working
2. Need to identify which channel customer used and based on channel different notification email will be sent.
3. How to add action button in notification email
4. How to handle error if there is no assignee
5. For any status changes or comments, do i need to use ScriptRunner Listener 

Thanks in advance for your help