1) We prefer to use Latin, Greek, Hebrew, Arabic, Sanskrit, etc., because these languages carry tremendous power that is missed by reciting things in "plain English."
You can pray in English, which is effective when one's supplications are sincere. However, to utilize a prayer in Latin, Greek, Hebrew, Arabic, Sanskrit, etc., with sincerity amplifies one's creative effort and produces magical results. This is similar to the difference between speaking to an audience acapella or using a microphone system.
Therefore, we must not be lazy, but do our best to use efficient and expedient means to attain stronger results.
2) There are different complexities because each prayer is a formula. Each has mathematical purpose, and we know that mathematics constitutes the world of intuition, the world of the Being.
In synthesis, take your time in learning the prayers that help you most. This is why we have a small print edition of the
Gnostic Prayer Book, which makes it easier to recite these prayers in order to eventually memorize them.
Each prayer is a weapon and a defense for the soul. Therefore, if the forces of darkness take great pains to inflict suffering on sentient beings, then we must be even more diligent in combating such forces.
Thus we must thoroughly study and apply these practices.