iPhone 4 (1349) upgrade the system without close NVRAM,stock on recovery mode

[GUARDIANANGLE]

I used the powdersn0w function of the software to downgrade the iPhone 4 (1349) from 7.1.2 to 6.1.3, but then I rashly used the software's Latest IOS (IOS 7.1.2) to upgrade the system without close NVRAM. After the upgrade, the system turned on and automatically entered the recovery mode, and I couldn't enter the system normally. I tried to update and restore it with iTunes, but I still couldn't enter the system. Later, I read the document carefully and found that I needed to close NVRAM. But now when my device is connected to Mac and chooses to turn off the NVRAM function, it prompts me that I can't enter DFU mode. What should I do? Please help me🙏

[LukeZGD]

if you cant enter dfu mode (broken buttons or something), you can use the dfu ipsw option in restore/downgrade to force the device to dfu mode. then from there, you can clear nvram. then restore the device to 7.1.2 again