Here is an answer to the second question:
Most people unintentionally will chant that mantra by hearing it as song, will there be any consequences?
http://literature.awgp.org/book/Gayatri_Sadhana_the_truth_and_distortions/v2.2
Q.1. Are there any restrictions on Gayatri worship?
Ans. There is a prevalent belief that the right to worship Gayatri is exclusively restricted to the Brahmans or the so called “Dwij” (which is traditionally considered synonymous with “Brahmans”, a caste in India). This is a gross misconception. If there is a dispute on the basis of caste only Kshatriyas will be entitled to Gayatri Sadhana as revealed to Vishwamitra, who was its rishi. His descendants will be well within their right to lay claim to their ancestral right . But such an argument would be nothing but childish. If persons living in India alone claim the right in respect of Gayatri what will happen to those Indians who have accepted citizenship of other countries? If Gayatri Sadhana is regarded only for Hindus, a ban will have to be imposed on those scientists who are conducting research in this field in foreign countries. In fact, in this age of intellectual freedom it is ridiculous to talk of such absurdities. Gayatri is the manifestation of the Creative Power of God; and like the sun, water, air earth etc. everyone is entitled to derive benefit from it. The concept of proprietary rights is applicable to only material objects. Creations of nature are accessible to all in equal measure. Endless benefits (Gayatri kalpavrikcha) can be enjoyed by invocation of Gayatri by all human beings irrespective of their social status. Every religion has its Supreme Mantra like Kalma of Muslims, ‘Baptisma’ of Christians, Namonkar of Jains, Om Mani Padme Ham of Tibetan Buddhists. So also in Indian religions tradition there is only one Supreme Mantra, Gayatri Mantra.
It is foolish to say that Brahmans, Kshatriyas, Vaishyas, Kayasthas etc. have different Gayatris. This bane of discrimination on account of high or low caste should not be allowed to enter into and pollute the spiritual environment in which there is one God, one religion and one source of knowledge. Gayatri is also the key to the invisible Cosmic Consciousness. An ancient Indian practice required compulsory admission of children to schools (Gurukuls) for learning spiritual concepts and practices. Here, the student was initiated by the spiritual preceptor (Guru) through this very Gayatri-Mantra, irrespective of his social background. As a matter of fact, the Shikha (tuft of hair on the crown of head) symbolises Ancient Indian (Bhartiya) culture. All Hindus traditionally keep Shikha as constant reminder to them to nurture high and noble thoughts. As such, Shikha itself represents Gayatri, which entitles all to the worship of Gayatri.
Q.2. Is it true that Gayatri Sadhana is permissible to a particular caste only ?
Ans. The concept of caste is grossly misunderstood in the modern society. Ancient Indian Culture did not relate the caste system to one’s parentage or ancestry. In those days, defaulters of basic codes of social conduct were deprived of normal civil rights. They were compelled by the society to undertake specific duties along with deprivation of the right to worship Gayatri. The caste of a person thus denoted the field of his activity rather than his parentage. Denial of worship was, therefore, a punishment to the guilty. In the present context, the codes for “social punishment” have changed. Work-assignments have also undergone a sea-change. Under these circumstances, all human beings, owing their existence to the one Supreme Being, are entitled to worship Gayatri irrespective of their ancestry, parentage or belief.
Q.3. Do Brahmans have a special privilege to do Gayatri Sadhana?
Ans. The professed proprietary right of Brahmans (by birth) on Gayatri worship is ridiculous. Credit for embodiment and elaboration of mysticism of Mahamantra Gayatri goes to rishi Vishwamitra, who belonged to Kshatriya caste by birth. Thus, even if the caste is considered essential for Gayatri worship, the Kshatriyas should have priority over other castes. The concept of Brahmanism has an entirely different connotation. A Brahman is one who conforms to the wisdom of Brahma (Brahmaparayan) and has an exemplary character. Only such persons of refined character can derive maximum advantage from Gayatri worship. It has been said that Gayatri is Kamdhenu of Brahmans. In several Sanskrit couplets, Dwijs alone have been described as entitled to worship Gayatri.
Traditionally, the words Dwij and Brahman have been considered as synonymous. In this way each Dwij or Brahman was supposed to have the exclusive privilege of worship of Gayatri. Does it mean that individuals belonging to other castes were scripturally prohibited from worshipping Gayatri?
The confusion has arisen because of misunderstanding of the meanings of words like Brahman, Dwij and caste, which are being misconstrued as hereditary distinctions conferred by God on various classes of society. Nothing can be more absurd than considering the Creator as discriminative and partial, making people take birth in a family of high or low caste.
When scriptures declare that Gayatri is kamdhenu of Brahmans i.e. Gayatri fulfils all desires of a Brahman, they mean that any human being who diligently aspires to be a Brahman by following righteousness in thoughts, words and deeds gets an access to the benefits of Gayatri. That is to say, Brahmanism is a pre-requisite for Gayatri worship.As regards the world Dwij it literally means ‘born again’. The initiation to Gayatri is the spiritual birth of a person, who has otherwise taken birth as any other animal. This initiation or Diksha is like ‘Baptism’ amongst the Christians and is akin to admission in the primary class of the school of spirituality. The concept of caste has been grossly distorted, misunderstood and misappropriated by vested interests. In Vedic times, division of civic responsibilities into four classes of people who were given education and training pertaining to their respective assignments was considered expedient. Each of this class was referred to as a varna. In course of time, when successive generations began to follow the same profession varnas got ossified into ‘castes’. With the change in social environment, certain castes assumed greater prominence in the society and in order to retain their supremacy propagated the concept of caste by birth as a God-given status.