White to move.

For starters, when bad FEN/PGN is received, the system should automatically terminate the error rather than leaving it on your queue for you to terminate manually. Eventually it will do that, at least some of the time, but meanwhile perhaps it's best like this for debugging.

Now about your problem, I think the misunderstanding is that where it says "move analysis" it doesn't mean "move number" analysis, it wants to see an actual move, like "49...Kg6" — so what you're actually asking when you want to know White's best 50th move is, "What is White's best reply to 49...Kg6?" where 49...Kg6 is the move actually played in the game.

If you go to it in "puzzle mode" (i.e. set to move 50) it looks like this: Xie Jun vs Hort, 1995 — notice that when you click on "computer analysis" the move 49...Kg6 is already stuffed into the field. Now you need only click the Request Analysis button. (For better or worse, that makes our daily puzzle a breeze for computer hounds, as the answer is always a click away.)

There's another way to get the job done: if you go to Olga, position yourself on Black's 49th move and click the ENGINE link — you'll automatically get an analysis of that position, i.e. White's best 50th move. (Sure enough, White missed a win.)

All that being said, there's no reason why the software shouldn't be able to recognize simple requests like 50.? or 49...? to mean "What is the best move at that point?" I can work on making it behave that way.

1. Enter a FEN for a straight-up FEN analysis. (It doesn't even have to be from the game you're looking at, but you probably got it from using Settings->Copy FEN.)

2. Enter a move like 50...Rd1 or 17.Bxh7+ and it will give the best variation stemming from that move.

3. Enter an entire variation like "17.Bxh7+ Kxh7 18.Ng5+ Kg6" and it will show the best play after those moves have been applied.

4. Enter a simple move number, like "50.?" or just "50" and it will compute the best move for that move number. For black moves, type 50...?

5. Special "easter egg feature" — if you leave the field entirely blank, it will show you how the game would have continued with best play. That can sometimes answer the perennial question, "What's the finish?"

i am curious on their continuations on such basics as The Evans Gambit, The Modern Benoni and my favorite, The Immortal Draw Variation,

No it's not against the TOS per se, unless it's done for some wrongful reason, which would include cheating in our games, stuffing ballots, dodging infraction measures.

In the realm of trolling, it would be wrongful to make multiple accounts for the sake of simply being duplicitous, possibly to create the illusion that their opinion is shared (or even contested.)

"Requested 2017-10-13 23:40:57" 60 second eval (Completed)

But another one requested at 2017-10-13 23:41:25 is still going. I do not remember requesting the second analysis, when the first one was done, I looked at the result and was satisfied.

I was adding today's puzzle to my Friday puzzle collection. So, as usual, I opened the drop-drown menu listing my collections, typed "F" to go the collectoons beginning with "f" --