Direct Answer: A request is an invitation for your partner to change their behavior, which they are 100% free to accept or decline. A boundary is a statement of what you will do to protect your own well-being if an issue persists. A request depends on their cooperation; a boundary depends entirely on your own follow-through.
When we make a request, we are asking for cooperation. This is a vital and healthy part of any collaborative partnership. However, if our partner says 'No' to a request, we cannot force them without becoming controlling. That is where boundaries come in. A boundary is your own back-up plan.
No! Requests should be your first line of communication. You should always ask for what you need first. Boundaries are only needed when requests are repeatedly declined and the situation affects your core well-being.
Yes, that is what makes it a request. If the other person cannot refuse without punishment, the sentence has moved from a request toward control.
It can, but the moment a consequence is attached to force compliance, it stops being a request. A request leaves the other person free to say no; a consequence that punishes a no removes that freedom.