I140 Priority date is Oct 2021. Strategy to stay in USA till my priority becomes current

My approved I140 priority date is Oct 2021 and I am still with the petitioning employer. Lets assume my priority date becomes current after 10 years, then next 10 years I should be able to do H1B extensions or transfers with any employer and unlimited time right?

Do every employer need to file perm and I140 or I can ask the last employer ‘closed to my priority date becomes current’ to file perm and I140, port my current I140 date and then file I485 when ultimately priority date becomes current?

Every employer does not need to file PERM and i140. You can wait until the PD date is about to get current and then file the PERM and i140 (for the employer at that time).

Or you can return to the current employer whose i140 is approved when the GC date gets current.