Can't find info on 4.01 fw....

Hi guys,

Totally new to the scene. I've found a person selling a ps4 with 4.01 fw. But I'm not sure if it can be done as there is very little information about it. I've found plenty of info the 5.05 fw, but not the 4.01 fw.

Can anyone give me a very short overview whether this is good enough or should I avoid it?

Also are there any downsides to this fw compared to other versions?

Thanks ever so much!