EDIT so you can ignore the rest: Somehow I manage to continue with the process, but I´m stuck on the Fastloader section. I´m on the screen with the big START button, but when I run the adb commnad (fastloader devices), no response.
I made sure to turn on OEM Unlocking before preceding, and now the "FAILED (remote: 'Flashing Unlock is not allowed (THW.)')
fastboot: error: Command failed" message appears. Also, "adb devices" doesn´t show anything, yet "fastboot devices" show one device.
Original Message: Hi! I stumbled upon this amazing post but I´m having issues, so I was wondering if anybody could help.
Little backstory of why I´m here: So, I bought my phone two years ago, IN2015 and was working fine until two weeks ago when the screen turned green and had it replaced. The new screen´s fingerprint wasn´t working, so I contacted the technician and said I had to factory reset the phone, so the new finger print could be recognized. Not sure of how true is that, but I went on ahead and did that. Last night he gave me the phone back, but as soon as I started checking it, I noticed it was now IN2017 (I´m not too faithful with whatever he did to my "phone", if it is still mine). When I tried to restore my phone´s backup, the system gave me the warning that the backup was made using a newer software than my current one (made with 13 and now I have 12). So, that´s basically the reason of my visit here. I want to restore my phone to Global (for better updates) and restore my settings.
Now the issues. So, since starting the post, some stuff are expected to be known by users (and yes, I get it, *this is not a common-guy-like-me sruff*). For example, turning on Test Mode, disabling device driver signing and that, was something I had to Google and modify several aspects of my PC to get it to work (if it is even working, as I read that in Test Mode, there is a huge watermark and I´m not seeing it).
Then, when starting the MSM Tool, no devices show up. I´ve selected Other, my phone is connected and has USB Debugging enabled, yet, nothing shows up.
I´m still at step 1 and already having lots of issues

Is there a video tutorial using *this* guide I could refer to? Seemed straight enough, but guess I´m having a really hard time (also the stress factor of losing my stuff and/or bricking the phone).
Sorry, but if anyone could assist, I´d be thankful.