This page explains how your Pro licence works: deactivating, changing laptop, using two laptops, and how updates and version upgrades work.
If you deactivate your licence (e.g. from the licence management page or support), the app will revert to the free tier on that machine. Your data stays on your Mac; you just lose access to Pro features (unlimited properties, multiple CSVs per property, merge) until you activate a valid licence again.
Yes. Deactivate or remove the licence on the old Mac if possible (to free the slot), then activate your licence on the new Mac using the same licence key or account. If your licence is tied to a limited number of devices, deactivating on the old one allows activation on the new one.
It depends on your licence type. Some licences allow a limited number of active devices (e.g. one or two). Check your licence terms or the place where you purchased (e.g. Gumroad, website). If you're allowed two devices, you can activate on both; if only one, you need to deactivate on one Mac before activating on another.