After a full day of work on my Stilo, here are my updates:
I don't think that would cause any damage to the PCB.
Clean the PCB with electrical contact cleaner, then plug just the PCB (not the motor) into the wiring. Check if you can hear the relay clicking when you operate the blind switch.
Tried it but unfortunatlly the relay haven't done any sound

Looks like the PCB is dead...
Also check that the motor (without the PCB) works with an external power supply from the car battery. Reverse the polarity to check it works in both directions. Be careful that the white plastic gear wheel does not come out while checking the motor.
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This had worked. I connected the motor to an 12V output from my PC (I was lazy to go outside cuz it's cold in here) and worked in both directions when I changed the polarity.
With this in mind, I jumped into the car and started to disassemble all the roof lining this time.
I reattached the rear motor in place so I could operate it manually to (at least) have the blind pulled all the way back. It had rolled quite easily (I had lubrificated the motor).
Afterwards, I rotated the roof knob but it hasn't moved at all. I thought that with the blind pulled all the way into the back, tho roof would work. But it didn't
Thinking that it could be dirt on the rulers, I operated it manually as well to get it open, clean and lubrificated... I had tried to opened it before manually but just a few inches. Now, I tried to open it completely and it stopped after the first glass was lifted (the front one) and the last (the rear one) started to open. After a close inspection, looks like the drivers side isn't opening at the same speed as the passenger side (as i'm in PT, the drivers side is on the left side

).
I didn't want to push it to hard because of what happened to Austin.
With this in mind, I just closed the roof again (with the reset procedure) and placed the roof lining again.
I left the blind open and I don't think that I will be able to get it fixed until spring. I don't have a garage and the weather in PT is quite unpredictable

I don't want to risk having my beloved Stilo full of water.
I believe that the left cable is stuck at some point... But it's strange that the first glass opens up with no effort at all and in sync in both sides and then it stops completely.
As for the front motor not working with the switch, I will try the guide on cleaning the skyroof switch ->
https://www.fiatforum.com/stilo-guides/121463-skywindow-switch-cleaning.html If it doesn't help, at least it doesn't make any harm
