Does Wifi P2P require *both* android devices to be 4.0+? According to the android developer guide...


  "Wi-Fi peer-to-peer (P2P) allows Android 4.0 (API level 14) or later
  devices with the appropriate hardware to connect directly to each
  other via Wi-Fi without an intermediate access point"


Does this mean that both devices need to be 4.0+, or can one be a 4.0 device while the other is a (rooted) 2.x device?
"Normal WiFi" and "WiFi direct" are separate things. If you want to use the latter, the answer is yes: both devices must be supporting it. If, on the other hand, your question is whether there's a way to directly connect the two: there's always the "hotspot" feature, which was introduced already before 4.0. So one device (supporting this) could act as a WiFi hotspot, and the other could connect there as to any other WiFi router.