Yes, of course it is a workaround.
I only have one sheet of the project, so I can not connect it to anywhere else. For the long connector on the left side, all those global labels are supposed to connect to a sheet that was not part of the partial project you uploaded.
Yes, that is correct, but I can not connect them to a sheet I do not have, and therefore I used the connector to get rid of the warnings (temporarily).
Input pin not driven by any Output pins
messages have nothing to do with labels, but with the way pins are defined. If you read the line below it:
Symbol U1 Pin 2 [CP, input Clock]
That is an input pin of your 74HC161 counter, and if it is not connected to an output pin then your counter can not count. That means that on another sheet, a global label with the name In must be defined, and connected to an output of some other IC.
Probably not. I am not entirely sure, but as far as I know they are just labels. Whether you use them as an input, output, bidirectional or passive, is (I think) just graphical. ERC looks at the pins of schematic symbols (inputs, outputs, etc). The labels are just names that connect wires.
When you connect a global label to a net, the net will always get the name of the global label. You get a warning about the other name, but this is just a warning. I suggest you start a new and simple KiCad project to experiment with this. And then only go back to this big project once you understand how the labels work. Wit a small project, it is also easier to zip and upload the whole project if you still have questions.