On my opponent's turn, I have units on battlefield A, and there are no units on battlefield B. My opponent has 7 points and moves Draven, Audacious to battlefield B. Does he score 8 points if there are no units to win a combat? In case that I have a unit and he wins combat, does he score 8 points?

To answer your questions regarding Draven, Audacious and the scoring of the 8th point, we must distinguish between scoring via Conquer (a game action) and scoring via Triggered Abilities.

1. Opponent moves Draven to an empty Battlefield B (at 7 points)

Does he score the 8th point? No.

• The Action: When Draven moves to an empty battlefield, he Conquers it (Rule 446.1).
• The Restriction: According to Rule 448.1.b.2, if a player is at 7 points and earns their final point through a Conquer action, they only score the 8th point if they have already scored every other battlefield that turn.
• The Result: Since your opponent has not scored Battlefield A (which you currently control), they have not scored every battlefield. Therefore, instead of scoring the 8th point, they draw a card (Rule 448.1.b.2).
• Combat: Because there are no units at Battlefield B for Draven to fight, he does not "win a combat," so his triggered ability does not activate.

2. You have a unit at Battlefield B, and Draven wins the combat (at 7 points)

Does he score the 8th point? Yes.

• The Ability: Draven, Audacious has an ability that awards 1 point when he wins a combat.
• The Exemption: According to Rule 448.1.a.1, points earned from sources that are not Conquer or Hold actions (such as Draven's triggered ability) are not beholden to the Final Point restrictions.
• The Sequence:
  1. Draven moves to Battlefield B, contesting it.
  2. A Showdown occurs. If Draven wins the combat, his ability triggers.
  3. The ability resolves, awarding your opponent 1 point.
  4. Because this point comes from a triggered ability and not a Conquer action, your opponent reaches 8 points and wins the game immediately (Rule 322.1).

Summary Table

Note: This interpretation is based on Rule 448.1.a.1, which explicitly exempts non-Conquer/Hold point sources from the Final Point restrictions, and FAQ #8530, which confirms Draven, Audacious can win the game by reaching 8 points. I could not fully verify the exact card text against the retrieved rules.