Caster sugar has finer granules than regular (or "granulated") sugar. For cupcakes, you should be able to use regular sugar instead of castor without any detriment to the final product.
Yes you can but castor sugar is more expensive than granulated so it is a waste of money.
Castor sugar is a superfine form of regular granulated white sugar (also known as "berry sugar"). Substituting regular sugar in its place can be done for some recipes without any consequence. In other recipes, there can be a difference in the texture of the final product (i.e it may be more gritty instead of smooth).
Regular granulated sugar is used most often but some recipes also call for brown sugar.
You should be able to substitute granulated sugar doe castor sugar without any significant detriment to the resulting product.
Confectioner's Sugar (powdered sugar) has a completely different consistency and quality than granulated sugar. You cannot substitute one for the other.
Finely ground sugar is Castor sugar also called superfine sugar. Icing sugar is also a very finely ground sugar
One tsp is 5gm. 40gm of castor sugar is approximately 8 tsp.
Castor sugar.
Dissolving will depend on surface area. Castor sugar has a smaller particle than regular sugar. The smaller the particle the larger the surface area. Surface area: Regular sugar < castor sugar < icing sugar. Castor sugar should dissolve faster than the same mass of regular sugar but slower than the same mass of icing sugar.
Castor (or caster) sugar is a type of British fine sugar. It is called castor because its grains are small enough to pass through a sugar caster (sprinkler).
Instead of using jam for the sauce on spaghetti and meatballs cupcakes, you could use a vanilla pudding with red and a bit of yellow food coloring in it. Yogurt would work as well, but the cupcakes would need to be refrigerated. Or a simple powdered sugar glaze with food coloring.
flour and sugar
Taylor Mack Fine Cakes bakery in Columbus sell sugar free cupcakes.