Can import iSeries 4000 config (OS ver 1.3.x) to rSeries 5000 (f5os-a 1.5.2)?

Yes, it is possible to migrate/import from iSeries to rSeries.

In my view, F5OS would be our Kubernetes-based virtualizer, allowing us to create tenants in the same way we used to with vCMP guests. The BIG-IP tenant is managed in the same way as a vCMP guest is managed today on VIPRION or iSeries.

A major difference between rSeries and iSeries is the introduction of a new Kubernetes-based platform layer (called F5OS) with additional features, the new F5OS platform layer is leveraged in both VELOS chassis (F5OS-C), and rSeries appliances (F5OS-A).

You can find more details about the platform rSeries appliances F5OS-A - https://clouddocs.f5.com/training/community/rseries-training/html/introduction.html

You can find more details about the platform VELOS chassis F5OS-C - https://clouddocs.f5.com/training/community/velos-training/html/introduction.html

Compatibility matrix for creating BIG-IP tenants on F5OS - https://my.f5.com/manage/s/article/K86001294

For platform migration, I recommend using f5-journeys, which will help with UCS adjustments. Don’t forget to save the master key from iSeries and load it into the BIG-IP tenant on rSeries where you will restore the UCS. - https://github.com/f5devcentral/f5-journeys#readme

His link contains information that will help restore UCS files containing encrypted passwords or passphrases.

Display the master key on BIG-IP iSeries: f5mku -K

Rekey with the specified master key on the BIG-IP tenant in rSeries: f5mku -r key_value