Each spell has their own mythical version, separatedly. This is explained by the methods of obtaining mythic versions of spells:
Learning Mythic Spells: To learn a mythic spell, you must either select the Mythic Spellcasting universal path ability or the Mythic Spell Lore feat. In doing so, you unlock the secret of using your mythic power to amplify non-mythic spells you choose.
Mythic Spellcasting (Ex)
You can learn a number of mythic spells equal to your tier and can expend mythic power when casting them to enhance the results. To select a mythic spell, you must be able to cast the non-mythic version or have it on your list of spells known. Every time you gain a new tier, you can select an additional mythic spell. You can take this ability up to three times. Each additional time you take it, you can select an additional number of spells equal to your tier and you gain one additional mythic spell whenever you gain a tier.
Mythic Spell Lore (Mythic)
You can learn a number of mythic spells equal to your tier and can expend mythic power when casting them to enhance the results. To select a mythic spell, you must be able to cast the non-mythic version or have it on your list of spells known. Every time you gain a new tier, you can select an additional mythic spell.
Special: You can select this feat multiple times. Each time you select this feat, you must select different spells.
As you can see, all references are to a single spell.
The Mythic Spell Compendium from Legendary Games addresses this issue adding mythic versions of nearly all the lesser and greater spells, along with spells that simply didnt get a mythic treatment from paizo.
Quoting their page:
The Mythic Spell Compendium includes over 2000 mythic spells, including every spell from the Pathfinder Roleplaying Game Core Rulebook, Pathfinder Roleplaying Advanced Player's Guide, Pathfinder Roleplaying Game Advanced Race Guide, Pathfinder Roleplaying Game Ultimate Combat, and Pathfinder Roleplaying Game Ultimate Magic, as well as hundreds more spells from official Pathfinder products designed for the campaign setting and companion books. If they were not already published in Pathfinder Roleplaying Game Mythic Adventures, you'll find them here. All of them. It also includes hundreds more spells from some of the leading 3rd-party publishers for Pathfinder, including over 700 spells from Deep Magic by Kobold Press and over 100 spells from the Gothic Campaign Compendium and other products from Legendary Games.