Suggested answer:
(1) With reference to the following two examples from the corpus, it can be said that the difference in meaning between Ø freedom and the freedom is "freedom in general" vs. "freedom related to a specific group or thing", e.g.
...development towards the concept of freedom...
...fighting for the freedom of Belgium and other small nations.

(2) Examples of countable and uncountable uses of opportunity, coffee, experience, and glass:
...I was throwing away a wonderful opportunity.
Only lack of opportunity saved us from outright delinquency.
...sat down opposite the man and ordered a coffee...
I spent countless rainy hours drinking coffee and scribbling.
...answering questions at the dispatch box would be an experience he was unlikely to forget.
...he must speak from experience...
Edie walks in with a glass of ice water...
He sincerely believed that he would shatter like glass.

The indefinite article a marks the nouns as countable, while the Ø article marks them as uncountable.

(3) Information is found immediatly preceded by the indefinite article in contexts where it functions as a premodifier; information is an uncountable noun that is not determined by the indefinite article. An example from the corpus:
There is an information centre and a tea shop...

Animal is a regular countable noun and is preceded by the indefinite article in contexts where the noun typically refers to an unspecified animal, e.g.:
...an intense inner conflict is that an animal sometimes exhibits strange...

When preceded by the indefinite article, fruit functions either as a countable head noun or as a modifier of another noun, e.g.
Or is rhubarb a fruit?
...had been a fruit farmer...

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Read about articles here (determiners) and about countability here
Terminology: article, countable, definite article, indefinite article, uncountable