TV84 did it again!
The latest version of 1.08 downgrade (v5) keeps your "tweaks" to the model number when upgrading to 2.04:
* Connected to: TCPIP::192.168.1.75::INSTR
-> *IDN?
<- (Return Count:55)
Rigol Technologies,DG992,DG8A123456789,00.01.08.00.01
-> :PROJ:MODE DG992
-> *IDN?
<- (Return Count:55)
Rigol Technologies,DG992,DG8A123456789,00.01.08.00.01
------------- flash 2.04 and reboot -----------------
* Connected to: TCPIP::192.168.1.75::INSTR
-> *IDN?
<- (Return Count:55)
Rigol Technologies,DG992,DG8A123456789,00.02.04.00.00
Just to be clear, my serial is not 123456789 and my model according to the store invoice is not a DG992.