If you are making icing, yes. If you are making a meringue, no.
Vegetable Shortening
No
It depends on the recipe. Rolled fondant might be a better substitute for marzipan than poured fondant.
The brand doesn't matter but it has to be lard or shortening....
To make fondant softer, you can knead in a small amount of vegetable shortening or glycerin. Alternatively, you can try microwaving the fondant for a few seconds or lightly steam it to soften it up. Be sure to work in small increments to avoid making the fondant too soft or sticky.
absolutely.
If you want to make fondant at home, marshmallow fondant is much easier and simpler to make then traditional European fondant. All you need is 16 ozs of mini (mini!) marshmallows, two pounds of confectionery sugar, a sprinkle of water, and some shortening.
It depends on what you are baking or cooking. Vegetable oil can substitute in some cases. Although it will change the characteristic of your end product because vegetable oil has less "shortening power" than vegetable shortening. Butter can substitute too but you would have to increase the volume and there is the risk of burning depending on what you are making. Lard can substitute too. Its really hard to give an answer that is good, safe without knowing what you are using the shortening for. If you are frying something it is another different matter too.
Yes
Butter can be used instead of shortening for fondant. Other ingredients needed with this recipe include corn syrup, vanilla and salt.
Yes and yes.