Schlage Backset Adapter for 1-3/8" doors and/or 2-3/8" Backset

Just a part. The 40-152 is a Schlage installation component, not a lockset, latch, or trim. You order it alongside the lock it is adapting, and it is only ordered when the opening is 1-3/8 inch thick or bored at a 2-3/8 inch backset.

No. The Schlage 40-152 is a backset adapter used for 1-3/8 inch doors and/or a 2-3/8 inch backset, so it changes how the lock hardware fits the door prep. The Cal-Royal PDL-200 is a privacy door latch disengage tool in steel construction, used to release a locked privacy latch from outside. Both are Schlage-adjacent shop items but they do different jobs, and the PDL-200 will not adapt a lock to a 2-3/8 inch backset.

Depends what the opening needs. If the strike side is the problem rather than the backset, a template ASA strike such as the Cal-Royal ASA478 covers the standard commercial strike prep. For latch adjustment on a non-latching stop, ABH roller latches are the usual fix, the 1890 Series with a full lip cast strike and 5/16 inch adjustable projection, or the 1895 Series with a T strike and 1/2 inch adjustable projection. None of those replace the Schlage 40-152, which is specifically the backset and door thickness adapter.

No. The GMS KIT-PART04 is a collars kit for cylinders, used to take up the gap between a cylinder and the door face. The Schlage 40-152 is a backset adapter for 1-3/8 inch doors and/or a 2-3/8 inch backset, which is about where the latch bore sits relative to the door edge. A collar cannot relocate a backset, and an adapter does not set cylinder height.

They address the same thin-door problem from different directions. The Schlage 40-152 is a backset adapter for 1-3/8 inch doors and/or a 2-3/8 inch backset, letting the lock hardware match a lighter door prep. The Trimco 1268 is an anchor plate at 3-1/2 inch diameter, which reinforces at the mounting point rather than changing the backset. If the lock physically will not fit the prep, the adapter is the part in play.