A:AnswerYes. The HP 21x Gaming Display comes with a VESA mount 100 mm with included bracket. You would need a wall mounting that supported this standard VESA mount.
A:AnswerTo be able to use this monitor with an Apple laptop, you need an adapter from your laptop to the HDMI port on this monitor. This website will help you determine which ports are on your laptop and which adapter you need: https://support.apple.com/en-us/HT201736
A:AnswerYes it can. The PS4 has an HDMI port and an audio optical port. While HDMI can carry both video and audio, this monitor does not have built-in speakers. You’ll need an external audio source if you want sound, or you will want to plug headphones into your PS4 controller.