-- What are small capitals? How are they different than something set in ALL CAPS?

small capitals (usually abbreviated small caps) are uppercase (capital) characters set at the same height and weight as surrounding lowercase (small) letters or text figures. All Caps would not have the same height and weight.

-- Does your font have small caps? If not name a font that does.

Yes, ITC New Baskerville does. 

-- Ligatures? why are they used? when are they not used? what are common ligatures?

Two or more letters are joined together to form one glyph or character. 

They are used to represent specific sounds or words. They are not used in place of letters. Common ones:ff, fl, fi

-- Does your font have ligatures? If not name a font that does. 

Adobe Garamond has a lot of ligatures

-- Difference between a foot mark and an apostrophe?

Foot marks are usually straight and don't have curves and is used to mark time or feet. An apostrophe is used in punctuation to emphasize a phrase or word or to indicate a conversation. 

-- Difference between an inch mark and a quote mark (smart quote)?

An inch mark (double prime) is also used to mark time or inches. A quote mark is used to quote what people are saying. 

-- Hyphen, en dash and em dashes, what are the differences and when are they used.

The hyphen connects two things that are intimately related, usually words that function together as a single concept. The en dash connects things that are related to each other by distance of any range. The em allows an additional thought to be added within a sentence like (). Em dashes also substitute for something missing or can be used like bullet points.