In bhagvad Gita, God has given so many instructions, is it necessary for one to follow each and every one of them? Or just follow only a few of them?
You can follow many instructions in the Bhagavad-gita, but there is one which is the most important one, which should not be neglected. It is stated in the verses 18.64-66 where Lord Krishna says:
Bg 18.64 — Because you are My very dear friend, I am speaking to you My supreme instruction, the most conﬁdential knowledge of all. Hear this from Me, for it is for your beneﬁt.
Bg 18.65 — Always think of Me, become My devotee, worship Me and offer your homage unto Me. Thus you will come to Me without fail. I promise you this because you are My very dear friend.
Bg 18.66 — Abandon all varieties of religion and just surrender unto Me. I shall deliver you from all sinful reactions. Do not fear.
That is Lord Krishna's supreme instruction, his most important instruction which you can follow regardless of whether you follow some yoga process described in the previous Gita chapters or not, regardless of whether you want to get moksha or not. If you dedicate your life to Lord Krishna, take a refuge in him, ie surrender to him, your life becomes successful.
You can follow this most important instruction whether you want spiritual advancement and ultimately moksha, or you just want material advancement. To be a soul dedicated to Lord Krishna, taking refuge in him, is always beneficial whether for material or spiritual gain.
In Bhagavad-gita God has given so many instructions, is it necessary for one to follow each and every one of them?
Up to verse 18.66 Lord Krishna explained to Arjuna various types of yoga and religious practices, many instructions to follow, but then remarkable, even it may sound stunning to Arjuna and us today who are learning Lord Krishna's teaching in the Bhagavad-gita, He simply says to Arjuna "Abandon all varieties of religion and just surrender unto Me. I shall deliver you from all sinful reactions. Do not fear." Thus He is telling him to abandon all those things to follow and just to take refuge in Krishna, and he calms him by saying mā śucaḥ "don’t worry, don’t fear".
So Arjuna do not have to follow all those things, for him it's good enough to completely take shelter, ie to take protection or refuge, in Lord Krishna, and Lord Krishna tells him there's nothing to worry about because He, Krishna, will take care for him and protect him.
By the way, as far as I know, this verse of the Bhagavad-gita 18.66 Vaishnava traditions often emphasize to be the most important verse of the Gita, comprising the sum and substance of (the essence or gist of) the entire Gita, Vedanta and Vedic wisdom in general. In Vaishnava opinion that Gita verse is telling the final and ultimate goal to be achieved, it's the greatest wisdom and secret of all secrets of the entire Vedic teaching. Sometimes Vaishnavas even say that a person who did not understand that Gita verse and its importance or significance stays to be an ignorant in this world although he, perhaps, may be a learned Vedic scholar knowing all the Vedas, etc.
First and foremost, Krishna does not say he is giving Instructions throughout the exchange between Arjuna & Krishna, that we call as Hari or Bhagvad Gita. There are other Gitas that also follow a similar dialogue 2 way Q&A interaction; it's what is called Inner Seeking & Enquiry & guidance to that by a Guru, under a unique context & scenario. Krishna shares with Arjuna, the wisdom & knowledge, because he cares so much for Arjuna; dearest.
In BG, Vishnu/ Narayan avatar Krishna (Purna avatar; all kalas, roles etc) plays the Role of a Guru to Arjuna, but constantly refers to him as a Friend, my nearest & dearest Sakha. On the other hand in Yog Vashisth, Rama (not purna avatar) plays the role of someone disillusioned with life & existence seeking out the answers while Rishi Vashisth becomes the medium to channel the wisdom.
And during the same Hanuman (avatar of Shiva) plays the role of one devoted to & longing "Rama" even before he has met Sri Ram (when both were children)
These are all Leelas, for the Divine to Re-convey the Wisdom. Let's not make them like Moses 10 commandments of Shall vs Shall not or Abrahamic systems of polarization.
Why? Esp why BG? There's a conversation between Narada Muni & Lord Vishnu about how it will be difficult for people to have age, life, time, and ability to grasp Vedas & Upanishads to evolve in Kali Yuga, and is assured that not to worry, in next revision of Divine Wisdom mass download to the Earthlings he will make it simpler.
Similar Gitas/ dialogues have happened to expound wisdom; Ashtavakra Gita, Uddhav Gita (how many know of this one?) Guru Gita etc. A lot of Shiva - Devi / Parvati Q&As are the basis of various wisdom scriptures
So, Sanatana divine wisdom is never Instructions but Wisdom of cause, effect & guidelines and recommendations. That's why there is no "mandated" praying 5 times a day even though in vedic scriptures such things are recommended as beneficial.
Now, getting to following the wisdom expounded in BG; Take it as knowledge and with your Sincere Intention & Effort, apply what you can. That is your part - APPLY. Effort. with Sincere devotion. Take what's there in BG or any scripture as Wisdom of Life and apply it to living your life.
Now, given our human inability & imperfection of worldly dynamics (BG talks about imperfection inherent in nature of karmic complexity) it would be impossible to execute perfectly our karmas or execute perfect karma. Here Krishna says worry not, if you perform all actions/ karma sincerely while keeping me in your heart/ mind, surrendered to me, then whatever "karmic accounting that remains" He will take care of it.
- Why? At the end of BG, Arjuna is exhausted with all the wisdom & pros & cons and overwhelmed; as most humans are (and he has to play this role for BG to be relevant to people). So Krishna says worry not, come into my Sharan / become Sharnagathi (I am not sure if surrender accurately depicts the above 2 words).
This is the "meaning" & purpose of BG & the safety net that Krishna or the Divine offers a devotee; no matter what karma & paths they take over life times, in his SHARAN, they will be taken care of.
PS: I am not very good at "mugging & memorizing every BG or other scripture canto location etc, so if someone can fill it in for me that would be great. I am focused on true seeking, sincere understanding & correct interpretation / absorption and more importantly APPLICATION of the wisdom.
No, it is NOT necessary to follow ALL the instructions of the Gita. Sri Krishna clearly has given different options through Arjuna to all the spiritual aspirants regarding this:
12.8 Fix the mind on Me alone; in Me alone rest the intellect. There is no doubt that hereafter you will dwell in Me alone.[Indicative of the Jnana-Yoga]
12.9 If, However, you are unable to establish the mind steadily on Me, then, O Dhananjaya, seek to attain Me through the Yoga of Practice.[Indicative of the RajaYoga]
12.10 If you are unable even to practise, be intent on works for Me. By undertaking works for Me as well, you will attain perfection. [ Indicative of the Bhakti Yoga]
12.11 If you are unable to do even this, in that case, having resorted to the Yoga for Me, thereafter renounce the results of all works by becoming controlled in mind. [Indicative of the Karma Yoga].
It is very easy to say that Sri Krishna's essential teaching is 'leave all the dharmas and surrender to me. But as Sri Krishnaprem points out in His 'The Yoga of the Bhagavad-Gita', it is the MOST DIFFICULT advice to be followed which can be practised only at the culmination point of the spiritual practices,mand that is why it was given in the ending chapter according to Sri Krishnaprem.
The Vishnu-Sahasranama very rightly mentions that ' AchAraprabhavo dharmo dharmasya prabhur achyutah': Dharma is born from following the scriptural do-s and don'ts and the Master of Dharma is Sri Krishna.Only when the Vaidhi Bhakti becomes fully matured, one is able to leave all the dharmas and surrender to Him totally.