About the transition of current project from Excel to JIRA

[Praveen Chitturi]

Dear Community,

We're currently running an IT Project(Kanban method) where it is started initially to go with JIRA but due to several factors team inclined to use Excel to manage the Epics and corresponding user stories. We have completed first two versions of development and heading to one major version where the no of epics/user strories , no. of users will be quite high. So using excel and generating pivot tables are quite cumbersome. Thus we are planning to make transition from Excel to JIRA. 

With this I've few queries to discuss with community as below

1. In the current excel we are having external id for epics(gaps). When we are planning to migrate to JIRA, can we use External ID in JIRA and use that field through out the remaining project time as unique key for epic(gap) in JIRA as we can't change the existing epic reference in all our communications? Does External ID field is unique? 
2. We're having 2 statuses on EPIC(gap) one is the PMO approval status like gap need to be approved, gap approved , gap declined etc. And another status is spec status like Spec is created, spec need to be reviewed , spec approved etc. For this I'm planning to use workflow status for PMO approval status and use another dropdown custom field spec status. Could you please recommend does there any better approach to achieve that. 
3. We're planning to use EPICs creation in one project and another one project for development user stories to have different workflow statuses per project.  Does this approach is recommended. I didn't have the prior experience with these.

Regards,

Praveen