Third edition is pretty close to the second edition.
Not identical, but pretty close.
The 4th edition kinda turned into storyteller with d6 instead of d10.
Even more dice than we've been used to, TN is always 5. Not a fan.
The name's the same, but I'd argue it's a new system.
5th edition is similar to the 4th edition from what I understand, but I have not actually read it, I must admit.