A serial number and IMEI are similar, but have some differences. The serial number is a unique number assigned by the manufacturer (like Samsung) to help identify an individual device, like a phone, tablet, TV, and so on. For example, your phone's serial number will be different from every other phone Samsung has made. Serial numbers make it easier for the makers to organize and keep track of their products.
On the other hand, an IMEI is only used for phones or other communication devices. Depending on the carrier, your device will have either an IMEI. These two numbers are different from a serial number. They are used at an international or global level, not just by manufacturers. Both types of numbers can help network providers track down a device that has been stolen or lost.
Finally, a model number is a specific number that applies to a range of products (i.e., the Note10, Tab S4, etc.). The number will vary depending on the year the product was released, its color, the carrier, and some other factors. Every model that falls into that category (same color, etc.) will have the same model number. For example, certain S8 models have a model number of SM-G950W, whereas some S9s have a model number of SM-G960W.
Most Samsung phones support dual SIM functionality, with the Galaxy Fold there is an eSIM inside the phone that can be used as the second SIM. The eSIM that is included on the Galaxy Fold is not supported in Canada.