There hasn't been any episode where this happens and I know this because I've seen very single episode of Glee to come. Although, I do think you ay be mistaking it for a nickolodeon movie that was supposed to be considered the "new" (HSM) "High School Musical". It's called "Spectacular". It's has the same thing you described.
1x05 - The Rhodes Not Taken.
The Glee Episode In Which Finn Happens To Sing Jesse's Girl To Rachel Is Laryngitis
season 3 episode 10
Episode 5 ' The Rhodes Not Taken'
Finn proposes to Rachel at the end of "Michael."
Episode 1×05 "The Rhodes Not Taken"
The Glee Episode In Which Finn Happens To Sing Jesse's Girl To Rachel Is Laryngitis
season 3 episode 10
Episode 5 ' The Rhodes Not Taken'
Rachel sings with Finn in almost every single episode.
Finn proposes to Rachel at the end of "Michael."
Episode 1×05 "The Rhodes Not Taken"
If you are talking about season1, then no, Finn will not get Rachel pregnant on glee.
Episode 2 "showmance" p.s. Finn (two n's)
OF COURSE! Finn and rachel will always have feeling for rachel wen anything comes around them! im the glee exepert ask me anything??
There is no episode of Glee where Rachel dies.
It was featured in Pilot and Hairography, both by Finn and Rachel.
There is an episode on Glee called 'The Quarterback' which is a tribute episode towards Finn Hudson (Cory Montieth)