Any other type of brown sugar. Failing that, any type of white sugar (leave out a little and add a tbl of dark molasses/black treacle, if you have it). Failing that, your stuck.
Oats. There's also butter, golden syrup and demera sugar.
honey
Scones are usually made without sugar.
Honey
sweet
Yes
yes yes
Yes! Its the same thing but finer
Splenda instead of sugar.
Eggs are not a replacement for milk. Water may be used instead of milk in sugar cookies.
yes, they are the same thing
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.