What is the heart rubbish?
Why doesn't the verb have a 'tu' or 'vous' ending, 'restes' or 'restez'?
In the tu form of the imperative mood, the final "s" is dropped for regular -er verbs (and aller).
I have a problem with the usage of the right preposition, HELP!
Because of sous ? It's mostly idiomatic here, in french you stay, walk (or dance) under the rain. It may sound weird in english, but that's the way we say it.