Is it possible to return the posted speed and number of lanes of a highway segment using Google Maps API, OSM data, or any other stream (paid for or free)?
I will give you a method using downloaded OSM data, as the API is designed for editing and not for read-only. You will find more details on this on the API usage policy page of the OSM wiki. If you really want to use an API, you can look at the read-only APIs like the Overpass API. Several other methods could also work, depending on how you will use this data and which tools you like most.
Important note: this is a technical method, but there is no guarantee that the speed and number of lanes are present in OSM for the highways you are interested in.