Haven't flown Mavic Pro in 2 years...what is best/most stable firmware to upgrade to????

Since 2017 the firmwares on the MP have been riddled with glitches and issues that often make the MP unfly-able.  Upto Summer 2019 I was using an Android.  Problems were always with DJI's firmware and  Android versions of DJI Go4.  I've now 'upgraded' to an iphone where I've never had issues with the actual App on iOS.

Looking for some direction from an experienced flyer on whether there is a specific FW that I should AVOID.  Also: is DJI Go4 the required app still or will DJI FLY work also with Mavic Pro.  I'm using iPhone 11.  Thanks in advance!!

DJI Go4 is still the standard App for the Mavic Pro. So long as you update all software and both drone and RC firmware you should be  OK.  I had no issues with my Mavic Pro (Platinum, in my case) following this procedure from purchase until I sold it last year to get the Mavic2 Zoom.  I would avoid using the DJI Assistant.  I always did my updating over wifi.

If there is no gain in later versions stick with the one you have, ditto the app. The only time I messed with firmwares on my Mavic 2's was when I was trying to get controllers and drones matched up so I got no conflict warnings, yes plural drones and 2 controller for each drone.