Venser, Shaper Savant

• WOTC Official Reminder Textofficial rules
  Flash — You may cast this spell any time you could cast an instant.

• WWizards of the Coast2017-03-14
  Official Ruling
  If Venser's triggered ability targets a spell cast with flashback, that spell will be exiled instead of returning to its owner's hand.
• WWizards of the Coast2017-03-14
  Official Ruling
  If a copy of a spell is returned to its owner's hand, it's moved there, then it will cease to exist as a state-based action. It can't be recast.
• WWizards of the Coast2017-03-14
  Official Ruling
  If a spell is returned to its owner's hand, it's removed from the stack and thus will not resolve. The spell isn't countered; it just no longer exists. This works against a spell that can't be countered.
• WWizards of the Coast2021-03-19
  Official Ruling
  If a copy of a spell is returned to its owner's hand, it's moved there, then it will cease to exist as a state-based action. It can't be recast.
• WWizards of the Coast2021-03-19
  Official Ruling
  If Venser's triggered ability targets a spell cast with flashback, that spell will be exiled instead of returning to its owner's hand.
• WWizards of the Coast2021-03-19
  Official Ruling
  If a spell is returned to its owner's hand, it's removed from the stack and thus will not resolve. The spell isn't countered; it just no longer exists. This works even against a spell that can't be countered.

Rulings via Scryfall