Last night I watched the episode about the girl that was possessed sejak the Russia guy. Freaked me out BTW. But they advertised it as a new episode and I have not seen it before. But why was Charlie alive?

I believe it was an unaired episode from earlier in the season. I guess it didn't fit into their schedule, so they just aired it as a bonus episode. So, Charlie was still alive at that point.

The episode that aired is called 'Unearthed' and it was originally part of season 1. They ended the first season with episode 20, so this one that aired was like season 1's episode 21! Thats why Charlie is still alive, because all of the episode was before any event that took place in season 2 :)

Apparently, Monday night's episode, "Unearthed", was an un-aired episode from season 1. However, the press release for the episode suggests something different:

"While the girl's mind-bending condition intensifies, Walter dusts off some old lab video and hypothesizes the unthinkable, sending Olivia and Peter to investigate the bewildering case in an original "Unearthed" episode of FRINGE and here's another mystery: is it an unaired episode from Season One atau is it from an alternate universe?"

Read more: link

This was an episode from the first season that had never aired.

i think thet ep was from 1s