This is called siksa guru, and it is most certainly a very real consideration in making spiritual advancement. Most likely there are persons who are guiding you at present, and those persons are a type of spiritual guide or leader in your life. To accept someone in the role of guru, however, means that their guidance is accepted in an absolute manner by you. That is to say, even if your present practices are not yet so mature that you are eligible for diksa, you can still take shelter of someone whose instructions you accept in an absolute manner. This is of course a very `heavy' kind of submission to present unto another person, and therefore should not be taken in any light manner by you. But to answer your question directly, most certainly one can fully follow the instructions of someone, prior to being an initiated devotee.

Yes, if they are authorized by their spiritual master to perform this service, and if they are receiving knowledge in disciplic succession.

In practical terms, is it not a fact that members of the public receive knowledge of God through all types of preachers/sankirtan devotees? E.g. book distributors, those who are asked questions by the public, lecturers, etc. all 'represent' God's message. This category is sometimes called 'one who shows the path', or a vartma-pradarsaka guru.

As Srila Prabhupada always emphasized, association of the guru or a saintly person through 'vani' (i.e. their instructions) is more important than association through 'vapu' (personal, physical association). Even in the proximate physical presence of the spiritual master, it is the vani, or his instruction that is the most important. Therefore, especially when one does not get much opportunity for physical association, one should make all endeavor to regularly associate with the instructions of the spiritual master, through hearing or reading, meditating, discussing and by continuing to apply those instructions in our day-to-day activities.

Hearing is a powerful method, and thanks to modern technology we have the opportunity to hear tapes virtually anywhere and at any time. By making a very conscientious effort to hear regularly and attentively the instructions of the spiritual master, one can keep oneself always connected to his instructions. Maintaining a deep mood of service to the spiritual master and trying to execute ALL of our activities in accordance with his instructions so as to please him, makes that connection very strong and deep on the spiritual platform. Associating with one's godbrothers/ godsisters in the same service mood when such opportunity is available, enthusiastically trying to serve the spiritual master together, discussing his teachings and his glories - all these greatly support, enhance and revitalize one's constant connection with the spiritual master, allowing us to feel his presence always. If the instructions of the spiritual master remain always close to our heart, this is like !

being personally trained by the spiritual master as he resides within our hearts due to our love for him!

The confirmation of the spiritual master most certainly affirms his acceptance of you as his disciple, and so also have you accepted him as your spiritual master in your heart. However, although what happened is unfortunate, according to the teachings of our scriptures and previous acaryas, we learn that the formal diksa ceremony is an essential and vital event or milestone in spiritual life for a devotee. Initiation or acceptance and taking shelter of a spiritual master is essentially a matter of the heart; however, the formal ceremony of initiation and formal acceptance of a spiritual master is not unimportant either.

It is through the diksa ceremony that a devotee is formally connected to the guru-parampara and ultimately to Krishna . Therefore the scriptural recommendation is that one must accept the formal diksa initiation from a bona fide spiritual master through whom one is connected to the parampara. Taking initiation from another spiritual master will not hamper your feelings of devotion and gratitude to the other spiritual master, nor will it nullify that acceptance of the heart; rather the shelter and guidance of your diksa-guru should only support and strengthen your connection with the former relationship.