ok I’ve done all but 2 levels one been Unsanitary level which I’m stuck on, I know you can't loose all health I’m stuck on the 3 conveyor belts with the blue barrier and purple/pink zap things. what I want to know is if I get to a save point just before that bit and I end up dying can I quit the game and then reload it back to the point before conveyor belt and if I make it across without dying will I still get the achievement for total perseverance or does it have to be done in 1 go from start to finish?

It can be done through checkpoints in certain levels, not in this one.  If you are falling and quit the game out before you actually die you can reload your las checkpoint.  With the conveyor belt you can't do that though