Questions on Migrating configs from iSeries to RSeries F5s

When we migrate between different platforms ,  I plan on following the below procedure but have few questions 

1. From the iSeries platform (iF5-A(Active) and iF5-B(Standby)), need to take backups and move them to the /shared folder and edit the UCS file(bigip_base.conf for LTM and bigip_gtm.conf for GTM) by modifying the Management Ips, Adding new Vlans(as I want to have new subnet for VIPs), creating new self IPs for all the node subnets and edit the existing domain to a new domain(ex:ab.xyz.com to dc.xyz.com). Modified files are iF5-A.ucs and iF5-B.ucs.                                                                                                                                - We need to remove trunk config from the new UCS file(K50152613), so do we remove the full config including the config where trunk has all the vlans added along with deleting the trunk interface? We have to manually add the vlans and Trunks through F5OS?                                                                                          - How can we edit iApps as they are no longer supported? 
2. On the new R-Series F5s, Bring them up and configure them for HA. Now when I copy using "platform migrate"  On the R-Series rF5-A(Active) and rF5-B(Standby), 

   tmsh load sys ucs /tmp/iF5-A.ucs platform-migrate for rF5-A

   tmsh load sys ucs /tmp/iF5-B.ucs platform-migrate for rF5-B  I see that in the KB article, it saves the non compatible config in /var/local/ucs/platform_migrate_ignored_objects

           Based on this K82540512, Looks like interfaces, trunks and Vlans are not copied? Does it copy the VIPs, nodes, pool members without Vlans? and should we be doing this after manually creating the Trunks and Vlans on F5OS?

         3. Why do we need to do "modify sys crypto master-key prompt-for-password" 

https://my.f5.com/manage/s/article/K82540512

If anyone has done this successfully, please let me know how you did it and what issues you saw?

Thank you