[Android Q&A, Help & Troubleshooting] cyberx5:
HI, tbh i don't expect any help here this is not a common phone and what i'm doing is not common ... but why not try :D

I'm trying to unlock the bootloader on my VIVAX Smart Fly V550

My problem is that when i run

fastboot oem unlock

the output on the PC is

...

and then on my phone i get this message

Unlock bootloader?

If you unlock the bootloader,you will be able to install custom operating system software on this phone.

A custom OS is not subject to the same testing as the original OS, and can cause your phone and applications to stop working properly.

To prevent unauthorized access to your personal data,unlocking the bootloader will also delete all personal data from your phone(a "factory data reset").

Press the Volume UP/Down buttons to select Yes or No.

Yes (Volume UP):Unlock(my void warranty).

No (Volume Down):Do not unlock bootloader.

So i press Volume UP and ... nothing happens :(

If i press Volume Down it says

return to fastboot in 3s

and then it puts mi back to fastboot and on my pc the output is

C:\WINDOWS\system32>fastboot oem unlock
...
OKAY [ 7.285s]
finished. total time: 7.286s

If i run

fastboot oem device-info

the output is

C:\WINDOWS\system32>fastboot oem device-info
...
FAILED (remote: unknown command)
finished. total time: 0.004s

But

fastboot getvar all

gives this output

(bootloader) max-download-size: 0x8000000
(bootloader) partition-size:flashinfo: 1000000
(bootloader) partition-type:flashinfo: raw data
(bootloader) partition-size:userdata: 32000000
(bootloader) partition-type:userdata: ext4
(bootloader) partition-size:cache: 19000000
(bootloader) partition-type:cache: ext4
(bootloader) partition-size:system: 80000000
(bootloader) partition-type:system: ext4
(bootloader) partition-size:metadata: 2500000
(bootloader) partition-type:metadata: raw data
(bootloader) partition-size:nvdata: 2000000
(bootloader) partition-type:nvdata: ext4
(bootloader) partition-size:frp: 100000
(bootloader) partition-type:frp: raw data
(bootloader) partition-size:tee2: 500000
(bootloader) partition-type:tee2: raw data
(bootloader) partition-size:tee1: 500000
(bootloader) partition-type:tee1: raw data
(bootloader) partition-size:keystore: 800000
(bootloader) partition-type:keystore: raw data
(bootloader) partition-size:secro: 600000
(bootloader) partition-type:secro: raw data
(bootloader) partition-size:oemkeystore: 200000
(bootloader) partition-type:oemkeystore: raw data
(bootloader) partition-size:seccfg: 80000
(bootloader) partition-type:seccfg: raw data
(bootloader) partition-size:expdb: a00000
(bootloader) partition-type:expdb: raw data
(bootloader) partition-size:logo: 800000
(bootloader) partition-type:logo: raw data
(bootloader) partition-size:recovery: 1000000
(bootloader) partition-type:recovery: raw data
(bootloader) partition-size:boot: 1000000
(bootloader) partition-type:boot: raw data
(bootloader) partition-size:para: 80000
(bootloader) partition-type:para: raw data
(bootloader) partition-size:lk: 80000
(bootloader) partition-type:lk: raw data
(bootloader) partition-size:protect2: a00000
(bootloader) partition-type:protect2: ext4
(bootloader) partition-size:protect1: a00000
(bootloader) partition-type:protect1: ext4
(bootloader) partition-size:nvram: 500000
(bootloader) partition-type:nvram: raw data
(bootloader) partition-size:proinfo: 300000
(bootloader) partition-type:proinfo: raw data
(bootloader) partition-size:preloader: 40000
(bootloader) partition-type:preloader: raw data
(bootloader) off-mode-charge: 1
(bootloader) warranty: yes
(bootloader) unlocked: no
(bootloader) secure: yes
(bootloader) kernel: lk
(bootloader) product: KON6735_65U_L570S_L1
(bootloader) version: 0.5
all: Done!!
finished. total time: 0.151s

All in all i'm stuck

I have an idea to what's happening some manufacturers make it almost impossible to unlock the bootloader by disabling USB drivers when you boot the bootloader it might be something similar here where it disables the Volume UP button ... but besides that theory... idk.

I'll be extremely grateful if you have any ideas :)

Tnx :)