Dear Grandmapele,
We can do animal liberation, protect or save insects, make prayers and dedicate merit for long life, and purify negative karma related to short life all without initiation. In some lineages it is permissible to recite long life Deity practices without initiation but omitting the sections on self-generation, blessing offerings, or torma ritual.
To have the full impact of longevity sadhanas, it is necessary to receive the appropriate initiation. This will include a special blessing, making a connection with the particular Guru-Deity, transmission of the mantra, and if you're lucky, transmission of the sadhana and a commentary to the practice. There are initiations typically into either the long life practices of Action Tantra or Highest Yoga Tantra, with some Deities having practices that are transmitted for both categories, such as Amitayus. There are also special uncommon lineages of long life deities transmitted by Jetsun Manjushri to Je Tsongkhapa - Ganden Oral Lineage - such as Yellow Yamantaka and both the common and uncommon aspects of White Heruka.
We should strive to improve the scope of our motivation for doing such practices.