How best to manage fixVersions and status synching across ITSM and JIRA Product Backlog

[Ravi Tata]

Hi Community, 
At my company, we have many Products and many Customers(Organisations in this case).
Not all clients have all Products and not all are on the same version of the Products too.

We are looking at 'Improving how we support our Products to customers'.
Here comes JIRA ITSM, which seems to be the way forward

A bit about our how we are organised:
We have a Support team(Product support), and INFRA team(do devops, platform management, deployments, maintenance, upgrades etc), then we have 3 Product teams(working on feature enhancements, some level 3 support for products)

Each Product has its own Product Backlog, Support Team to use a JIRA ITSM proejct, INFRA to use their own KANBAN project.

There are 2 main use cases im trying to cater for:
1. 1 issue reported by 1 customer, post investigation impacting that 1 customer only.
2. 1 issue reported by 1 customer, post investigation impacting many customers.

We are pretty much adopting a model that follows this :
See
https://support.atlassian.com/jira-service-management-cloud/docs/how-agents-and-development-team-work-on-bug-reports-together/

Few questions - 
1. How do i set up what is mentioned in point #6 in the support doc above?
2. How can i manage and communicate fixVersions in such a way that, when a bug is fixed and is added to a fixVersion in the Product JIRA project, that it can be synched to the linked JIRA ITSM issue reported by our customer/s via Portal?


I look forward to your responses & hear some of the current practices you follow around these in your organisations.

Thanks in advance
Ravi