The requirement for the fuel selector to be set to L or R at shutdown is only for the R and S models I believe. Older 172s can be shut down and secured with the selector set for Both. However, the selector must be set for Both during takeoff and landing operations. Crossfeed valve are more commony used on multi-engine aircraft. We hardly use the crossfeed valve on our 172/R whereas on the 414 it's not uncommon to use it. Reason being that on the 414, the normal procedure is to feed each engine from the tanks on that side. However, slight differences in power setting can create an imbalance. To correct the imbalance the crew can take one of two actions: increase the power setting on the heavier side or crossfeed. On the 400 series twins, there are two individual crossfeed valves. One is the No. 1 engine and the other is No. 2. Crossfeed shutoff (emergency or otherwise) is handled by the Emergency Crossfeed Shutoff valve, located between the No. 1 and No. 2 fuel selectors. Due to the fuel system design on the 400 series, the only way to prevent fuel from moving from the high tank to the low tank on an uneven ramp is to actuate the Emergency Crossfeed Shutoff valve. On our plane, normal practice is to leave this valve in the closed position except during flight operations.
"When a man runs on railroads over half of his lifetime he is fit for nothing else-and at times he don't know that."