Ive been diligently reading and though I currently don’t understand much of it I haven’t seen this concept. I have intermittent power during storms so the thought is a ups just for the pi so it doesnt corrupt date from power loss. But what I would like to see or accomplish is power grid sensing so when the pi was running on back up power, most functions would be disabled until power was restored. then it would automatically enable the functions that had been disabled for power savings. Is this doable?
Yes, this is doable, and advised for any system that runs critical processes. Sensing a loss of mains power is simple with a transformer and a function can monitor the transformed voltage to determine if any functions should be disabled (upon power failure) or enabled (upon power return). There are several UPS systems specifically designed for a Raspberry Pi, but you could also design your own. There also exist many UPS systems for industrial control panels that can continually output 5 volts in the event of a power outage and these often have communication pins to indicate when power is lost and resumed as well.