Windows boot manager will always be there, until you reinstall OS without that. What does USB For legacy mean, how is that a way to check this? USB works in legacy and UEFI, so you lost me there.
Anyway, as mentioned above, I can change the other possible profile being used next, once you are 100% it’s not already changed
@Lost_N_BIOS The laptop doesn´t want to boot from my USB containing HBCD 15.0,and Windows says that it´s running on UEFI mode
You may need to learn how to boot from that on this laptop, maybe only possible via Boot manager at startup, then choose USB by name. Or may only possibly by BIOS exit page, choose USB by name, or maybe only if you move USB to top of boot list etc, many ways to boot to USB and that’s sometimes tricky on some machines.
Of course, if you already have booted to USB in UEFI mode, then you know how to do it on this system, at least for UEFI 
Here, try this one now
http://s000.tinyupload.com/index.php?fil…660856046280741
If it doesn’t work after this, then you need modified BIOS with this changed in setup instead, which I can send you too but probably best to wait for programmer to be in your hand if this is your only computer
I’ll check USB related settings in BIOS now and see if any maybe locked to UEFI only None caught my eye as being UEFI Only
Where does windows say it’s running UEFI Mode? I don’t think that’s a “Thing” Windows doesn’t run on UEFI or legacy, that’s a BIOS thing.
@Lost_N_BIOS this looks correct?
I know that´s in UEFI cause msinfo32 says : Bios mode : UEFI
vars2.zip (40.9 KB)
Reboot if you flashed in the other varsm2 already. MSInfo32 will always show UEFI, because you have UEFI BIOS (This is showing BIOS type, not boot selection or OS type etc), so not a valid checking method.
No changes,and the laptop is still on Warranty
The laptop is booting in UEFI,and the bios is now on legacy?
Then nothing left to do, unless you want to try to flash in a mod BIOS without a programmer in your hand and backup made?
If it allows the flash, or if we work around the error stopping you initially, but BIOS mod is broken due to security reasons, then you wont be able to fix it or boot until you get a programmer and SOIC8 test clip w. cable.
Best to wait really until you have flash programmer and SOIC8 test clip cable in your hand and full backup made with programmer ad validated by me to be a proper BIOS backup.
Please edit your posts if you need to add more comments, don’t make me have to ask you again this is the 8th time, thanks
Sorry, I don’t understand your last question?
What is your huge rush, what are you trying to do etc?
How can i revert the bios to the original?Can i use recovery method?
I want to let the laptop 100% original
Reflash stock BIOS
Yes, reflash stock BIOS and your back to square one again. You still never said what your goal here was??
If a BIOS update from Acer appears,can i update?Or it will brick my laptop?
Flash it now, what do you mean “appears” 
Download the latest BIOS and flash it now, you can get it here in the BIOS section - https://www.acer.com/ac/en/ID/content/support-product/6975
BIOS Update can brick a system at any time, but no it’s not a normal occurrence.
@Lost_N_BIOS Can you please close this topic?But don´t delete it,it can help anyone in the future,who knows the day of tomorrow… 
We’ll leave open, no need to close, as you mentioned maybe someone else will want unlocked BIOS and have programmer later or would be willing to test out mod BIOS via stock modified flashing methods etc.
If we close, then they’d have to ask to open, which you know means they’d just make a new topic instead, if they even used search before posting
Order yourself a programmer and SOIC8 test clip cable, it’s less than $6 total shipped, then once it arrives you’ll feel much better/safer about playing around 
I used acer website to reflash bios,now my bios is 100% original,right?
If u can sign the bios and put it in H2OFFT,it will brick,right?
Yes, if you flashed stock BIOS using stock method, then BIOS is 100% stock original. As for your last question, I am not sure what you mean. I cannot sign the BIOS, I can only modify it, and yes bricking BIOS is always a possibility even when you flash stock BIOS (every/any time)