Syncing project tasks from one cloud instance to another

[John Theofanopoulos]

Greetings,

Some context so you understand why I'm asking for a sync method:

- We have instance A which is a JIRA software cloud instance that my company uses,

and then we have

- Instance B which is a JIRA software cloud instance of one of our developer contractors (not controlled by me but I have access)

Now, during the development cycle, the developers in instance B were working on our projects and were creating tickets,comments,epics etc.

How can I do one-time sync and get all tickets and history from Instance B and add onto Instance A ?

Also what is the best way to have continuous sync from Instance B to instance A when it comes up to specific project?

Additionally can I also have sync from a new Instance C to instance A when it comes up to specific project?

Again, I do not have administration privilages apart from Instance A and I'm looking for a manual method or a free plugin to do so.

P.S: The point of this sync is to grab all tickets and it's history from Instance B, add it into Instance A and have the 'original ticket history' in my Instance A. 

Keeping in mind that the project was created and finished in Instance B few months ago, this time I just want to export/grab all tickets and history from Instance B and add in same project in Instance A for historical purpose (audit from higher management etc).

But it would also be nice to know how can I have continuous sync for projects that I choose from various instances to mine.

Thanks