Is the 9.7 iPad Air 2 64 GB WiFi +cellular unlocked to GSM network
Per the specs,
Carriers (for WiFi + Cellular Model Only)
Cellular and Wireless
Can you use it without adding a mobile carrier to it?
Yes, you can use it as a Wi-Fi only tablet.
wondering if this is compatible with the apple pencil?
Here’s the compatibility list. Doesn’t look like it to me: