Jaya's Immolating Inferno

• WWizards of the Coast2018-04-27
  Official Ruling
  You can't cast a legendary sorcery unless you control a legendary creature or a legendary planeswalker. Once you begin to cast a legendary sorcery, losing control of your legendary creatures and planeswalkers won't affect that spell.
• WWizards of the Coast2018-04-27
  Official Ruling
  You can't target the same target more than once to have Jaya's Immolating Inferno deal more damage to it.
• WWizards of the Coast2018-04-27
  Official Ruling
  Other than the casting restriction, the legendary supertype on a sorcery carries no additional rules. You may cast any number of legendary sorceries in a turn, and your deck may contain any number of legendary cards (but no more than four of any with the same name).

Rulings via Scryfall