Where is Expose Prey in the Hunter talent tree?

Survival tree, row 5, column 2. You need 20 points spent in Survival before you can learn it.

Is Expose Prey new in WoW Forever?

Yes. Expose Prey has no Classic 1.12 counterpart.

Rank	Effect	Source
1	Grants your melee and ranged attacks against enemies afflicted by Hunter's Mark a 5% chance to allow an activation of Mongoose Bite. Lasts 10 sec.	client
2	Grants your melee and ranged attacks against enemies afflicted by Hunter's Mark a 10% chance to allow an activation of Mongoose Bite. Lasts 10 sec.	client

Tree: Survival, row 5, column 2. Needs 20 points in Survival first. The earliest you can finish all 2 ranks is level 31 if you put every point into this tree.
Unlocks: Lacerating Strikes (requires Expose Prey at full rank).
Competes with: Resourcefulness, Survivalist's Discipline, Strider Kick in the same row.

Expose Prey is new in WoW Forever. Nothing in Classic 1.12 does this for Hunters.