Student or Learner
If you have any question(s), raise your hands.
Are both the singular and the plural suitable in the sentence above?
"If you have any questions" or "if you have a question"
I would still say "Raise your hand" if addressing a group. Each person will only raise one hand.
These questions can go either way. It's unlikely that anyone will have both arms waving in the air.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.