Need clarification on I140 portability rule


My I140 got approved on Apr 2015. I received a H1 based on approved I140 from Apr 2016 to Apr 2017.

Per new I140 portability rule which is effective from 01.17.2017, can I change employer based on previously approved I140 and new employer can apply for extension or will new employer have to file perm and I140 again and apply for extension?

Please help.

They will have to initiate the process from scratch, but the only thing that will remain unchanged is your priority date.

Thanks. Can the new employer extend the H1 and then apply for fresh perm and I40 or perm and I140 has to be approved with new employer first to extend H1? Also, what is the end to end processing time for Perm and I140 with and without premium?