Vietnamese crunchy rice

Crust formed on the bottom of the pot deliberately? You put the rice in a very hot stone pot after cooking and let it sit a bit so that the crust develops (Korean version). Or you add some butter up front and cook the rice longer than necessary so a crust develops in the cooking pot itself (Iranian version). Many ways to do this, but I agree it's divine :-)

They could have been individually deep-fried grains of pre-cooked rice. A salad of these are known in Thailand as nam khao tod, and I expect that the Vietnamese have their own version.

About types of rice, in fact, there are too many types of rice. They can be categorized by their characteristics: "sticky" (like that in sushi rice), "fluffy" and "fragrant" (like jasmin rice). A type of rice can be both sticky and fragrant, or fluffy and fragrant, or just sticky or fluffy. The rice in fried rice dishes is not sticky rice.

There is no "uncooked rice fried in oil". All rice in fried rice dishes are cooked.

To make the fried rice crunchier, you use cold cooked rice. So you should place cooked rice in the fridge. Cold cooked rice is less likely to stick together when you fry. When the moisture in the rice grains evaporates, you have crunchy fried rice.