What wierd is the scene with the mouth-stitched-shut guy and the eyes-stiched-shut actually takes place before Saw 3.
From what I know heres some important parts in chronological order.
Jigsaws soon to be child was killed.
Jigsaw was diagnosed with cancer.
Jigsaw got in his near fatal accident.
Jigsaw began his “saving”
Jigsaw recruited Amanda Young who was the first to survive his test.
Jigsaw and Amanda prepared the bathroom trap.
Saw 1.
Saw 2: All scened with Daniel Mathews (cops son) in the trap occur before the scenes involving Jigsaw.
Eric Mathews gets trapped in the bathroom trap.
Eric escapes the bathroom trap by breaking his foot and has a brutal encounter with Amanda.
Jigsaw “cleans up after Amanda” by putting Eric in a cell and keeps him alive for the Saw 4 trap.
Amanda begins to defy Jigsaw’s orders by making the traps unlivable.
Chain and stitches trap.
Jigsaw, Amanda, Hoffman, and mouth-stiched-shut guy all prepare for Jeff and Riggs traps.
Saw 3 and Saw 4 occur almost simultaniously: the revengeful man Jeff Reinhart and Lieutenant Rigg are going through their long traps at the same time. Jeff completes his and kills Jigsaw and Amanda causing Lynn (his wife) to die. Rigg completes his which actually means he failed his and caused Eric to finally die. Rigg shoots the mouth-stitched-shut guy (Art Blank) who was Jigsaws business partner and was forced to prepare much of Riggs trap.
We finish with the moor with Detective Hoffman listening to Jigsaws message.
Somewhere in there Hoffman became Jigsaws second apprentice, definately before Saw 3. It is unknown whether Rigg survived or not. The strange man who was paired with Eric in the trap left Rigg to bleed to death. This man was not in any danger and it reminds me of how Jigsaw put himself in the bathroom trap. The man obviously got out easily and was not electrified when Eric was killed. I sorta think he might be Detective Hoffman but he’s all wet and they all look alight to me but it would make sense if he was.
I hope this helps you understand the plot, sorry if I’m wrong or I confused you even more. Good luck!