My problem is that i need to use unreal engine 3 for rocket league map making but the lowest unreal engine i can install is 4.0.5
Only UE4 is avable via luncher. Free version of UE3 (without C++ programing access) was called UDK so search using this name. Epic don’t host installs anymore too so you need to use alternative sources, there thread in UE4 forums which provides alternative links (first on top don’t work go to bottom)
Note that you won’t find any Ue3 support here (your quastion most likely wont be anwsered) as well as Epic don’t support it anymore you need to ask on UDK forum section for any help there higher chance you will get help there