You get parts of these swords from puzzles during the first half of the game then Ada will comment on restoring the blade at the blacksmith. Then you need to enchant it inside the castle’s lab and choose blade’s stats.
You don’t need to fight bosses twice to get both scenes. From day 1, each boss gives you a special heart item. Use it to unlock both scenes with the corresponding in the gallery.
The type of scene depends on Ada’s lewd level. After a certain threshold, you‘ll get only lewd ones. Decrease Ada’s lewd level or make a pure playthrough to get the normal ones.