is it possible that a 1700 beats a GM

Yes, it is "possible". I'm sure you can read between the lines.

"Possible" is a very low bar. It's possible the entire earth explodes tomorrow.

It's very hard to have a "bad day" and play 400 points below your rating. Anything 400 or lower means something is very wrong, like you're very sick or dying lol.

Ben Finegold talked about a game that he has played against a 1000 rated player and he was losing until the very end and then 1000 rated player blundered and lost the game.

When I get angry that I lost couple of games in a row because of stupid blunders I wouldn't be surprised if my playing strengths goes down by 400 points in those moments.

Anything is possible so yes

a 1700 rating player can beat a 2500 rating GM at odds of 1 in every 100

What kind of question is this lol

A 1900 player beat Alireza Firouzja (currently rated 2778) in an over-the-board, classical time control rated tournament game.

@1
Yes, in 2.6 games out of 1000
https://wismuth.com/elo/calculator.html#rating1=1700&rating2=2500 

Sure, you can play random moves angerly as you smash your phone against the table

When I said "very sick" I just meant the person has lost their will to play well. Being irrationally angry is the same i.e. you don't care about playing good moves anymore.

So maybe I should rephrase it... if you actually care about playing well, it's very hard to play 400 points below your rating. The handicap for a GM to lose to a 1700 would have to be great enough to take away the GM's will to play good moves e.g. they're dying. IOW it becomes a silly question.

Other than taking away someone's will, you can distract them. For example lighting them on fire heh.

Firouzja was only 15 and dealing with the stone-age political extremism of his home country.

Ben Finegold, during a live stream a few years ago, answered a similar question.  His answer was something along the lines of "if a 1200 plays 40 perfect moves, I make a draw, but the likelihood of a 1200 doing that are extremely slim".

While he used 1200, the point remains largely the same.  To draw a comparison: could a middle school backup basketball player beat a Division 1 starter in 1-on-1?  In theory, it is possible, but the likelihood is so small that you will likely never see it happen.

A 2000, or a 2200, beating a GM happens from time to time.  It almost never happens with someone below 2000.

Well, first of all, GM is a broad term. GM can be someone pretty old that is possibly around 2 200-2 300 at the time. This GM can lose if he has a bad day. 

As for 2 500 rated GM, I am sure that something similar happened in a game, after all, the history of chess is long, and there has been many games so far.

Something close to this, but not quite is this:

https://en.wikipedia.org/wiki/Aman_Hambleton

To quote:

He played on the reserve board again at the 43rd Chess Olympiad. He lost to the 1937-rated Rijendra Rajbhandari in the first round,^[9] but won his last four games to finish on 4½/7 (+4–2=1).^[10]

I am sure there have been worse defeats, but they are certainly very rare.

Judit Polgar lost to a 1700 in a rated OTB game, although it might have been G/30 or G/60.

That's interesting. If it is G/60, technically it is still a classical game if I am not mistaken. 

@PawnTsunami

By the way, I am not sure if chess could be compared to basketball though. In basketball, if much better player makes a terrible mistake, he is losing 1-0, and as they will either play to 11 or 21, he has to make many more mistakes in order for much worse player to be victorious. 

In chess, one mistake can be so terrible that it loses the game. Smaller margin for error in many cases. So I am sure, there were some very bad defeats out there, but of course it happens once in a million games.

It is worth noting that Aman wasn't a GM at the time.  He had just become an IM and the guy he lost to reached a peak over 2100 during that event (earning a FM title).  So while being an upset, it was only a 300-400 point gap as opposed to an 800 point gap.

There is this for instance:


This is more than 600 point gap. And if there is this, there are certainly even bigger upsets. I just found it on quora.

Agreed, the analogy is not perfect but it does demonstrate the problem.  The question is asking if it is possible for someone that is effectively a semi-professional player lose to an amateur.  Sure, it is possible, but highly improbable.