1. LrMobile doesn't have any tethering capability. If tethering to the iPad is possible, the photos would go into Apple Photos, and then LrM could receive copies (you have to enable auto add and specify a collection). This is the main risk area for you - can you tether to the iPad so new photos go into Apple Photos?
2. Yes, in LrM.
3. Yes, though this could happen sooner if your iPad is connected to the internet. So if you have a sim card and mobile data is enabled, LrM will start uploading. Alternatively, over wifi connections there is automatic uploading to Adobe's servers and down into Classic.
If I use a laptop computer with Lightroom CC Classic installed, I assume that I could tag images and then export those to my desktop Lightroom later. Is that correct?
Just looking for a way for my clients to see the image captures and then choose which one they would like to keep. Then do all of the editing back at my home (desktop) computer. But I would have to be able to transfer the "tagged" images from a laptop to my desktop.
Yes, to take work on one computer to another you use the command File > Export as Catalog, which creates a small catalogue of the selected photos. Move that to your other computer and File > Import from Another Catalog,