eSIM

Yes, it is.

You have two choices: contact your cellular carrier and see if they offer that service (check the prices), or, if your iPhone is unlocked, you can contact an abroad carrier who can provide eSIM service.

For any further questions, I suggest that you read this support article:--> Using Dual SIM with an eSIM - Apple Support

Regards

Giulio

Usually, yes.

Here is how to use eSIM on eSIM capable iPhone models, including on most iPhone 12:

About eSIM on iPhone - Apple Support

That article also includes how to transfer your current carrier plan into the eSIM, which would give you the option to load two plans, with the SIM available for roaming. Or you could keep the SIM, and load the eSIm for roaming, though eSIM plans and service can be less common in some areas of the planet.

You will need to have an iPhone that is not carrier locked:

How to unlock your iPhone for use with a different carrier - Apple Support

Yes, that is possible. This is, among other things, what the function is made for. For example, you can buy a plan in the place you are traveling to that offers eSIM, use it on your trip - when you travel home again you can delete the eSIM card again.

You can read more about how to use Dual SIM/eSIM here:

Using Dual SIM with an eSIM - Apple Support

You can. You would need to acquire a eSIM from a carrier in the country you will visit. It would probably be a prepaid plan.

Be aware, some carriers do NOT offer the eSIM option on prepaid or pay as you go accounts.

Make sure the phone is carrier unlocked. Otherwise a SIM (eSIM or physical) from a different carrier will not work on a carrier locked phone.