Why does she know everything about Luna’s life? Why does she have photos of Ámbar and everything related to the Benson / Valente family?

One theory is that she’s someone who was trained by Sharon. Yes, Sharon had a small redemption at the end of season 3, but we only saw that scene with Ámbar. We don’t know what happened after that or whether Sharon spoke with Luna or Alfredo in these years.

YES YES YES YES YES YES. I'M LITERALLY REWATCHING IT EVERY YEAR. I STARTED LAST WEEK AGAIN.

I'm currently in s2 ep5 IT'S THE ONE WHERE LUNA SINGS THIS SONG IN THE OPEN AND SHARON FINDS OUT SHE'S SOL I'M SO EXCITED.

First off, instead of simply saying that Simbar is in a long-distance relationship because Ambar is busy elsewhere (and that Valentina can't go back for this 4th season), just like Simon, well apparently that's too difficult and they absolutely have to make Simon in couple, so from what we know they're going to say that Simon and Ambar broke up to set him up with some other girl who came out of nowhere.

And according to other leaks...

Luna isn't going to end up with Matteo but with Simon... So Lumon would be endgame.

This then led me to the thought that Sunny Benson would easily be mixed up with Sunny Baudelaire.

Then I realized baby Sol and Sunny Baudelaire do look similar.

I mean here's baby Sol

And here's Sunny in a similar outfit

Even BOOK! SUNNY reminds me of Sol

So Alfredo knew Ámbar was adopted by Sharon, and therefore was his granddaughter. Yet he didn’t care about her until he thought she was Sol. He was always talking about it was unfair he didn’t get time with his grandchild (Sol) when Ámbar was right there and he just… didn’t care. Oh and when he found out Luna was Sol he threw a huge party and showed her off to everyone, but not with Ámbar

That would definitely leave out a lot of frustration while watching. But I also think it might take away the tension in the show. If I remember correctly, there were a lot of times where they almost found out the truth, it wouldn’t be as tense to watch if we didn't know. At least that's what I think.