Building a new Project database BUT using a subset of issues & attachments from the Original

[HRaman]

I have an existing Project "MAIN1" (from backed up version) from July 2021.

I would like to create a New database "NEW2" up to a different point in time, June 2020 only. 

What is the easiest way to achieve this?

I tried deleting the entries from the existing Project database version up to June 2020 and exporting the CSV file. Then restoring the CSV file but the problem with this method is that the sequence of issue key numbering is skipped and it is not acceptable.

Furthermore, with CSV the attachments are not imported. I have no idea how to do this import if the original "MAIN1" database is not available. 

Any help on this?