Rocket League Collector's Edition
Yes just make a party and invite them. Or just join another friend that invites you
You can play Rocket League in single player or local multiplayer without a PS Plus subscription
Online multiplayer requires a PS Plus subscription.
Yes, you can play single player against bots by yourself, or in local multiplayer without going online.
The Game of the Year edition contains all the content from the Collectors edition, plus a bonus theme and avatar icons for your PS4.
Up to four players at a time can play in offline splitscreen.
The Collectors Edition includes three complete DLC packs, as well as four additional vehicles and a limited edition art print.
Thank you for your question katavion, Yes, you can play Rocket League up to 4 players offline split-screen.