[Galaxy A3, A5, A7, A8, A9 Q&A, Help & Troubleshoot] wurlitzer99:
I'm going to write a long post. But I believe it will help a lot of people having a similar problem.

Long story short - problem solved! but it took much of my nerves (and time).

I'll start with the "warranty". The so-called Samsung "warranty" which basically worths nothing!

Calling Samsung international service center, they "informed" me that I must contact Samsung Vietnam, where I bought the device, although I am not there anymore... Needless to say the local dealer in my country refused to take care of this situation, saying Samsung's warranty is regional based, rather than international... which means, only Samsung in the original country where the device was sold in, are responsible for the warranty (and therefore repair!). I had a chat with a Samsung Vietnam representative, who just kept saying "I'm sorry", and refused to let me sent the device out to them for repair! asking me to "bring it to them", although I noted him a few times that I bought it as a tourist and I am not in Vietnam anymore.... Thank you Samsung !! From now on every traveler in the world will know they basically have NO WARRANTY if they buy any Samsung device in a "foreign" country while traveling abroad!

Now for the solution:

I started by letting the device staying connected to the charger overnight, which didn't help. With the OS now installed, I realize that the battery was NOT CHARGED ! it was completely drained, although connected to a charger for long hours... So, know from now on that if your boot data is corrupted, it may cause the device NOT TO CHARGE THE BATTERY at all. Luckily, my desktop PC could use the device while connected to it although the battery was empty, until the problem was sorted out. I did get a crash on my MAC tough (Log said it was USB related), while using Smart Switch, so one option is that it could not supply enough power to the device to keep it keep working at all, or working correctly... So my suggestion is to use a desktop Windows PC in this case, which can potentially provide more power to a device with 0% battery power.

After scratching my head, and considering removing the front panel for replacing the battery (a very risky procedure) I decided to keep on investigating....

I followed a youtube video who suggests that you should install Smart Switch on a PC, choose "reinstall driver" from the menu, restart the PC, then use Emergency Recovery and Initialization, enter the phone model number in the search box (as appearing on the back of the device) , and once it recognizes the model, also to enter its serial number. Here's the video:

https://www.youtube.com/watch?v=1yXQUFrEWg4

This basically brings up a popup message saying Smart Switch detects a compatible firmware for this device, and is about to download and install it. It then asks the user to do the Power+Vol Up+Home push combination trick + pushing UP once the page is loaded in order to "Continue" and bring up the ODIN Download screen, which worked for me if did that as soon as the device shuts down (in the middle of the bootloop). As I couldn't make it load at all with no charger connected, I had it connected to the charger, and once I saw the Smart Switch message asking to do the push combination, I quickly connected it to the computer using another cable which was already connected to the PC USB port on its other end.

Somehow, I could at last make Smart Switch finally start downloading the firmware from the web, and the device again disconnected (bootlooped), but luckily Smart Switch didn't care about it disconnecting, and kept on downloading the firmware. At about 85% of the progress bar state, I could find the downloaded firmware on the temp folders, which are described in this thread:

http://forum.gsmhosting.com/vbb/f777/samsung-firmware-download-belongs-his-serial-number-2038404/

I had to make sure it wasn't still downloading, and watched the "last modified" state of the file to make sure they are not being downloaded anymore. CAUTION: although the AP was not downloading anymore, I know it was probably not good as ODIN couldn't verify it when I tested it. USE ONLY SMART SWITCH !

I quickly copied the folder to which the app extracted the BL and AP files it downloaded, and finally had an officialy bootloader (BL) image, which I could use in ODIN in order to reupload a correct, "official" bootloader to the device....

I hoped the device won't bootloop in the middle, but luckily ODIN was fast enough to send the image successfully, with a "PASSED" status, and the device booted with a nice "Samsung" logo directly to a System Recovery page!

What I exactly did, was loading ODIN, then loading ONLY the BL file into the BL field in ODIN, having it verifying it, and once verified I connected the device, and as soon as ODIN recognized it, pushed START. It managed to upload the image into the device in a few seconds! It seems then, that the bootloop was not caused by a bad battery, but as a result of a corrupt upload of an AP image through ODIN - or because I possibly was using an incorrect version when I tried to upload an AP files to the device on my first attempt to flash it.

Note that I did search for the correct, compatible AP file, by country and model (on Sammobile) but it didn't' work (stuck at 50% in ODIN) ! so I really suggest everyone TO ONLY USE SMART SWITCH if they want to be sure that the correct firmware is being used, and avoid similar situations...

I then deleted the temp files from the PC (the actual ones which were in the temp folder), reinstalled the drivers from inside Smart Switch (just in case), booted the device to Download mode (WHICH DIDN'T BOOTLOOP this time), let Windows installing the drivers (checked in Device Manager), then restarted the PC, and ran Smart Switch again. I repeated the procedure of loading Emergency and Initialization, entering the model and serial number, having it fully downloading the firmware (again) from the web, and installing the firmware into the device. This time it completed the process, and I finally had the device installing and booting into a fresh version 6.0.1 of Android!

Hope it helps!