1. Is it still possible to obtain Ace of Spades in Destiny 2?

Yes, you can still receive the Ace of Spades in Destiny 2 as of Witch Queen. The exotic hand cannon may be purchased at the Tower's Exotic Kiosk for 1 Exotic Cipher, 125,000 Glimmer, 200 Etheric Spiral, and 1 Ascendant Shard.

2. Is the Ace of Spades useful in Destiny 2?

Yes, the Ace of Spades is the most powerful weapon in the Crucible. It has the most kills from a single weapon in PvP, and it is the second most used gun in both Crucible and Trials of Osiris.

3. In Destiny 2, is Ace of Spades helpful for PvE?

No, and anyone who tells you differently should be dismissed. Of course, it's suitable for typical PvE stuff. When confronted with encounters of that difficulty, every weapon is available. It is outclassed in every metric by other PvE weapons, including legendary hand cannons like Fatebringer.