Yes, but a restaurant is a noun, not an adjective. All nouns have a gender, masculine or feminine. All adjectives have four forms: one masculine singular, one feminine singular, one masculine plural and one feminine plural. Normally the feminine form is created by adding an e to its masculine correspondent, and the plurals by adding a s to the singular forms: vert - verte - verts - vertes.
But some adjectives already end with an e in its masculine singular forms. They do not add another e to make it feminine but keep the same form in masculine and feminine: riche - riche - riches - riches. These are said to be invariable in gender. Liquide as an adjective is like this.
You've left us hanging here! And the link you provided below now goes to "Pronouncing the N in Spanish". So here is a new link: https://www.lawlessfrench.com/pronunciation/forbidden-liaisons/ . I'm thinking it's because "jus" is a singular noun???
After a singular noun you are not supposed to pronounce a liason.
You can read about more forbidden liasons here: http://french.about.com/library/pronunciation/bl-liaisons-f.htm
What you are talking about is the French verb "liquider" (to settle), as in "to settle" or "to liquidate" an account. When the verb is conjugated, the 1st person and 3rd person singular forms of the verb are "liquide". So you see, hints for words can cover a lot of territory, so you have to choose wisely.
No, singular nouns followed by a vowel are among the "forbidden liaisons" in French. http://french.about.com/library/pronunciation/bl-liaisons-f.htm
I tried, "Juice is a liquid", thinking that "le jus" can mean juice in general. DL didn't accept that. I guess the article was needed, i.e. "Le jus est un liquide." But wouldn't, "Le jus est liquide" mean "Juice (in general) is in liquid form", or in effect "Juice is a liquid."
It doesn't completely not make sense (though my interpretation may be kind of stretch). I also thought it was jeu, and liquide meaning cash. So the sentence could mean something like "the game is cash" as an adjective or "the game is to make cash." Does a sentence like that actually make sense in French?