In option 1A, suppose the 2" lav drain (starting at the lav san-tee, the lav trap arm would be 1-1/2") didn't go down to the 3" line just below it. Suppose instead the 2" lav drain entered the floor system and connected horizontally to the 2" tub drain, upstream of the wye where the tub drain joins the shower drain. And further suppose that said wye has its outlet size increased to 3". That would be a way to let the lav drain wet vent the tub, the shower, and the WC.
Presumably you mean 2A. Just Reach4's comment, which is in reference to the venting of the laundry sink and standpipe. The laundry sink is the upper fixture on the stack, so the stack can vent it. The standpipe needs its own dry vent taken off (via an upright combo) before it joins the stack, and that dry vent can connect to the stack, at least 6" above the flood rim of the two fixtures, which is called a revent.
In option 2A, the terminology is that the shower is dry vented, the tub is wet vented by the shower, the lav is dry vented, and the WC is wet vented by the lav.
The horizontal and vertical distance limits that apply to 2A, assuming a 2" tub trap (the waste and overflow can be 1-1/2"):
5' of pipe run and 2" maximum fall from the shower trap outlet to the upright combo where the shower dry vent comes off.
5' of pipe run and 2" maximum fall from the tub trap outlet to the wye where the tub trap arm joins the shower drain.
6' of pipe run, counting both vertical and horizontal sections, from the closet flange to the wye from the lav drain joins the WC fixture drain; no limit on fall.
Cheers, Wayne