It looks like it is game over:
" Nintendo of America, Inc. has filed a takedown request under the Digital Millennium Copyright Act (DMCA). I received the request on my personal email, so I'm complying with their requests.

There will be no more AM2R updates, and no more releases under any platform.

Thank you for the support during all these years."
Source: http://metroid2remake.blogspot.com/

Damn.
Well, at least we got the game, I guess..

You forgot the title of that blog post.
"No future for AM2R"

Hey guys.

I would liike to see all endings, unfortunately I think I don't have skills to unlock them all by myself. Could someone either tell me how to edit the save file or upload it with whole gallery unlocked?

Here is all the screens:

http://i.imgur.com/97BHYmQ.png

http://i.imgur.com/QvgtRFX.png

http://i.imgur.com/WCukqaU.png

Only three endings? Are they time/item completion-related (like in other Metroid games) or each one is received after beating the game on each difficulty level? If the latter, then I could try getting the oher two, because I already finished the game on Easy and got the first ending.

Yes it all depends on time and item completion.

Time only, actually. Under 4 hours for the helmetless picture and under 2 hours for the armorless one.

Thanks for the info.

Also, I found a save editor on the internet. I was able to edit the game timer and beat the Queen again, and again. Although I still saw the first ending after the credits (likely something else is also responsible for ending pictures), the proper endings have been unlocked in the gallery. I know that's cheating, but problem solved.

If you are interested, then you can download the save editor here (requires Java to work):
https://mega.nz/#!IQ9h3JCY!gkm7OqaWBpVGIr5HyGAHQUyPs5lD65w2a5pZ42uqfR8

Of course, backup your save in case you mess up.