As verbs the difference between remain and remained
is that remain is to stay behind while others withdraw; to be left after others have been removed or destroyed; to be left after a number or quantity has been subtracted or cut off; to be left as not included or comprised while remained is (remain).
Is remains singular or plural?
Singular. remain. Plural. remains. (plural only) The remains of something are parts of something gone that are still here.
Which remains or which remain?
is that remain is state of remaining; stay while remains is what is left after a person (or any organism) dies; a corpse.