There are no clear rules on when or when not to pronounce final consonants in French.
You don’t pronounce the final "r" of infinitive verbs that end in "er" such as habiter, visiter:
habiter
visiter
However, you do pronounce the final "r" of infinitive verbs that don’t end in "-er":
dormir
sortir
pouvoir
You also pronounce "r" in the following words:
mer
pour
toujours
In French, you generally don’t pronounce the final consonant of frequently occurring (daily) words:
logement
appartement
petit
grand
blanc
Pronouncing the final "s" of "plus"
You don’t pronounce the final "s" of "plus":
- in the expression "ne...plus":
Je n'habite plus [ply] le quartier.
- before a word beginning with a consonant:
Ce logement est plus [ply] petit.
You do pronounce the final "s" of "plus":
- in the expression "plus de"
Ce logement a plus [plys] de pièces.
- before a word beginning with a vowel:
Ce logement est plus [plyz] original.
- for the (+) sign in mathematics. You say [s] before consonants and [z] before vowels.
Il faut un bureau plus [plys] deux chambres.
Ce logement compte deux pièces plus [plyz] une.