Can I connect a single remote to multiple devices?

Certainly, but know that there are trade-offs with this pattern of use. The supported configuration for this is to have a remote that you carry with you from your home to your office. The remote is paired with a device in your home as well as in your office. Each of these devices is configured independently of each other, but your remote will connect to the first device it sees. This allows you to use a single remote in two places.

However, be aware that you will have difficulties if you connect a single remote to two different devices in the same location. If your phone and iMac are connected to a single remote, there's no way to know which of the two devices your remote will control.