You also get the additional MQMs if you use pay with miles to pay the fare difference when you purchase the ticket. It's a variant of FCM and the ticket (alsmot always) is a G A P fare.

How many miles did you pay for the upgrade? Was this an offer on the app or at the time you purchased the ticket? Or did you call DL and request a mileage upgrade award? The Z fare class looks to me like it should be a FCM upgrade using pay with miles.

I was always under the impression that if you “bought” the upgrade (with $ or miles), and the original ticket was paid using $, that...

1- You recieved the 200% MQM bonus if you “bought” the upgrade prior to T-24/check-in,

2- You did NOT recieve the bonus if the upgrade was bought after T-24/check-in.

Reason being, the system assumed you were complimentary upgraded after T-24 and processed it that way. Someone please correct me if this is incorrect.

Prior to T-24, if you buy the upgrade by paying a fare difference or taking a special offer on the app to pay some additional money, you should get the additional MQMs, although usually it's 150% not 200% as upfaring into FULL F of FULL C is likely to be very expensive. The same is true if instead of paying such price differences with money, you use miles instead.

You generally don't get additional MQMs for upgrades purchased (with miles or money) at check in or at the gate, meaning T-24 or closer to the flight.

However, you can also upgrade DL tickets at some fixed number of miles depending on your fare class and the route. These mileage upgrade awards are normally not eligible for the additional MQMs. Usually they require some round number of miles, maybe 45,000 rather than 18,900 and they normally book into some inventory class that looks like a variation on award ticket inventory, not regular paid (but discounted of course) fare class, for example Osomething where O is a "saver"/"low" business class award ticket and OU would be a free elite upgrade (on routes that permit them) although DL has been changing its fare classes again.

Probably, but you could also pay lots more to upfare to FULL F or FULL J/C to get 200% MQMs.

Yes, MQMs should be based on the G fare you purchased: 150%.

The 8900 miles looks like a FCM pay with miles upgrade with an alternative cost of about $89 to upgrade. My understanding is that doing such an upgrade before T-24 should result in the 150% MQM earning as your ticket was probably reissued in G class or whatever the new code is for deeply discounted domestic FC, which I guess now means Z class. You'll earn MQDs based on the fare that was paid with money.