Sorry but that's not correct. 'forceLimits 4' and 'forceLimits 1' both do exactly the same thing. P4 used 'forceLimits 4', but they changed the parsing (I think in P5) to 'forceLimits 1'. All current versions including P4 will accept either variant. The poser interface provides no way to change the 'forceLimits' flag (a py script may be able to do it).

The "Use Limits" switch in the Figure menu is something complately diffrent, and has no effect on the 'forceLimits' flag (but will override 'forceLimits 0'). The "Use Limits" switch is a global setting, it applies to the whole document. The flag itself lives in the 'doc' section of the pz3, it is named 'useLimits', and accepts a value of 1 for on, and 0 for off. When 'useLimits' is set on all channels in the scene will use limits, even those that have 'forceLimits' set to zero. When 'useLimits' is set off, a channel will use limits according to the status of its 'forceLimits' flag.

A long time ago someone (I know who, but I'm not sayign) said that 'forceLimits 4' and 'forceLimits 1' had different effects, and every one just accepted that without bothering to check if it was correct. It's the number one Poser superstition!