Please explain Release files purpose

[cystbear]

According the doc I have:

SD card file placement

/SAROO/update/ ;Store firmware for upgrade. 
                   ; FPGA: SSMaster.rbf 
                   ; MCU: ssmaster.bin

I have downloaded all releases 0.1 -- 0.6 and have next files (tree)

./
├── firm_v0.1
│   ├── SSMaster.rbf
│   ├── ramimage.bin
│   ├── saroocfg.txt
│   └── ssmaster.bin
├── firm_v0.2
│   ├── SSMaster.rbf
│   ├── ramimage.bin
│   ├── saroocfg.txt
│   └── ssmaster.bin
├── firm_v0.3
│   └── SAROO
│       ├── BIN
│       ├── ISO
│       │   ├── ULTRAMAN.BIN
│       │   ├── kof95.bin
│       │   └── readme.txt
│       ├── mcuapp.bin
│       ├── saroocfg.txt
│       ├── ssfirm.bin
│       └── update
│           ├── mcuboot.bin
│           └── ssmaster.bin
├── firm_v0.4
│   └── SAROO
│       ├── mcuapp.bin
│       ├── saroocfg.txt
│       └── ssfirm.bin
├── firm_v0.5
│   └── SAROO
│       ├── mcuapp.bin
│       ├── saroocfg.txt
│       └── ssfirm.bin
└── firm_v0.6
    └── SAROO
        ├── mcuapp.bin
        ├── saroocfg.txt
        └── ssfirm.bin

What I can see:

• starting 0.3 there is no more SSMaster.rbf file for FPGA update
• starting 0.4 there is no more ssmaster.bin file for MCU update

Latest update (0.6) contains only three files one of themssfirm.bin. What it stands for? Also as soon as I can understand mcuapp.bin it's SAROO application which MCU runs and its config saroocfg.txt.

So my questions are:

• how I can update my SAROO board to latest FPGA bitstream/hardware?
• how I can update my SAROO board to latest MCU firmware?
• what ssfirm.bin stands for?

My board is V1.37C from KK DIY