What is the English word describing a long thin loaf of French bread, which crust is appetisingly golden and crunchy, and the bread inside is light and fluffy?
It's the same as it is in French: a baguette
In the UK we call it a stick of French bread (baton or baguette are a bit "middle-class")
It could also be ficelle.
It is described in English language dictionaries as a long thin loaf of white bread with French origins. It is usually pronounced as two syllables, with the tonic accent on the last syllable: Bag-ETT. http://www.merriam-webster.com/dictionary/baguette https://en.oxforddictionaries.com/definition/baguette
In France, some people will pronounce it as three syllables: bag-ET-te.