Can we connect 4 HomePod together?

You can create stereo pairs. You could make two pairs and then they can all be played in sync

•  If you’re setting up a second HomePod in the same room, you’ll see an option to use both speakers as a stereo pair.

Set up and use HomePod - Apple Support

Yes you can add as many as you like. I’m not sure about them being in the same room using the same name, you might want to have livingroom1 and livingroom2 for example.