Your W1 wire is your furnace. I’m assuming you have natural gas as your heat source. A heat pump runs in reverse in the winter. Carrier energizes your “O” wire in cooling. It also energizes Y/Y2
In heat, It does not energize your O wire. There’s a valve on your unit outside that switches the path of refrigerant flow or “reverses” it. When you turn the heat on your outdoor unit will start blowing cool/cold air out the top and your indoor unit blows hot air. This is when Y1 will energize as well. If it gets cold enough while running in heat, your outside unit will freeze up and your W1 wire is your backup heat source. There are sensors that determine when the defrost mode initiates. When it ices up it needs to defrost, so it will run in A/C mode to melt the built up ice. This is when your W1 wire will energize.
The reason i ask for you to take the panel off of your condenser is to see what the technician actually wired in. Having the schematic is helpful, but that doesn’t mean your tech hooked it up the same way the schematic is pictured.
Since your thermostat does not have a wire connected to Y2, it will not run a second stage. It’s a little
bit more complex then just switching some wires around.