I am using MB asrock h110 hdv re3.0. I tried the mod and followed the instructions but still couldn't lower the ME FW in the bios to 11.6. Has anyone mod yet? please give me. please

What is your current ME FW version? Even with mod BIOS with 11.6 ME FW, usually the BIOS or normal flash method is not going to downgrade ME FW, you need flash programmer or to do pinmod.

ME FW 11.8.50.3425
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how to downgrade ME FW down. I missed updating to bios 7.50: '(

You may need flash programmer, or to do pinmod (See "E.1 section" here), usually this will be the case as ME FW downgrade has rules/restrictions so even if Instant Flash would update ME FW if in BIOS, it probably cannot and would not downgrade it.
You can try though and see if it works, if not ME FW would just remain same. Please tell me what BIOS version you want used, and what ME FW version you want used, and I will make you a BIOS with that ME FW version in it, then you can test via Instant Flash and see if it downgrades ME FW for you or not.

If you do Pinmod method, you need to dump FD with FPT before you reboot, edit it and flash it back, otherwise if you reboot you will have to do pinmod again. Tape off all other pins, so you don't fry your audio!
You need ME System Tools V11 package from here in section "C" - Intel Management Engine: Drivers, Firmware & System Tools

And here's how to use FPT to dump FD and flash it back. To edit FD to unlock it, see the guide above where I showed you the E.1 method, in section "B" see spoiler two, image 1-2 and that is how you edit the FD to unlock it before you flash it back in.

I want to use the version ME FW 11.6.0.1126
asrock h110 hdv re 3.0 Bios version 7.20

Here is BIOS with ME FW 11.6.0.1126, test flash with Instant Flash and see if ME FW downgraded or not. - http://s000.tinyupload.com/index.php?fil...611622254884295
If not, you can now use this BIOS as ME FW source and flash ME FW region with FPT and info above, once you unlock your FD, otherwise you need flash programmer to downgrade ME FW
If you get flash programmer, DO NOT program this BIOS in, this is stock BIOS, you need to dump your BIOS contents with programmer and replace ME FW region from this file to your dump then reprogram back to chip.

Unfortunately, it's still impossible to downgrade ME FW

Yes, as I mentioned/expected, very unlikely that Instant Flash would downgrade your ME FW due to ME FW has rules and restrictions on downgrading
Your only option is pinmod or flash programmer.

Unfortunately I don't know how to make pinmod or flash programmer
 I also have to use google translate to talk to the admin. I'm very stupid. help me

I gave you link to instructions above how to do pinmod.
Flash programmer you have to order online, you need CH341A + U Type Flat IC Extractor, this costs around $5 USD shipped, let me know if you need me to link examples on ebay.
Here is guide on how to use flash programmer - [GUIDE] Flash BIOS with CH341A programmer

Talk to admin?? Sorry, not sure what you mean there. Anyway, here, one last thing we can try

@badbon - Here, try this BIOS Flash via Instant Flash. After flash ME FW will be disabled, so you wont see version or you will see N/A or 0.0.0.0 etc. - http://s000.tinyupload.com/index.php?fil...771921978915596
Once flashed in, clear CMOS. Then boot to BIOS and load optimal defaults, then save and reboot back to BIOS and make any other changes you need.
Then save and reboot to windows and flash ME FW using FPT and this BIOS file using command below. FPT MUST be ran from Admin CMD prompt, put BIOS file into same folder as FPTw.exe and then run the command below
If success and it lets you flash ME FW then run second command and reboot. Then using Instant Flash, flash back in the BIOS I sent you at post #6

FPTw.exe -me -f H11MHDV37.20
FPTw.exe -greset

If error, show me, and try rename file to H11MHDV37.bin and try again, same command as above, unsure if the .20 extension will cause issue with FPT or not.
Also, do not run FPT from any folder with underscore in the URL, best to run from folder on desktop if you are not sure.
Show me error you get, if any, and make sure I can see top of window/title bar too so I can be sure you are using Admin CMD prompt.