Is it necessary for a soul to attain enlightenment in order to attain liberation after death?
Or is it sufficient to just focus the mind on God in order to attain liberation after death(even if the soul fails to attain enlightenment during lifetime), as Lord Krishna says "Focus your mind on Me. I promise you, you will come to Me".
As some people are of the opinion that "No enlightenment means No Moksha".
Yes, you have to attain moksha if you want to permanently escape from the ravages of worldly life. Focusing the mind on God leads ultimately to liberation after many births. Even if such a person fails to gain liberation in one birth, he will eventually succeed.
Moksha only stable value
One who aspires to overcome the thick darkness of ignorance should never seek contacts that are contrary to the fourfold end of life (Dharma, Artha, Kama and Moksha). Of these four ends, Moksha alone is accepted as the really stable value to be sought; for the other three are subject to the destructive force of Time.
Srimad Bhagavata Purana IV.22.34-35
Liberation can be attained without Enlightenment.
Enlightenment could be a subset of Liberation.
Both of them contains Daivi sampada, which is acquired via Bhakti.
Typically related with death. Getting beyond the 3 modes, leads to liberation & the rebirth doesn't happen:
BG 14.20 - Having transcended these three modes (sattva, rajas, tamas) which are the origin of the body, the embodied one, becoming free from birth, death, old age and sorrows, experiences Immortality.
Typically Rajas holds back due to its attachive quality. The one who is without desires (born of Rajas), eventually would get liberated.
BG 6.27 - That yogi of pacified mind only attains the ultimate happiness, whose Rajas(passion) has calmed down, identifying with sinless(desireless) Brahman
A thought may generate a desire and hence a sin - Ramana Maharshi.
Thoughtlessness is the way to liberation [BG 6.25]. Rajas is the cause of sins.
Hence we can infer that the liberation might be possible by moving higher in sattva OR lower in tamas. Everything is liberated anyways, at end of the cycle:
BG 9.7 - O son Kunti, all the beings go back at the end of a cycle to My Prakruti. I project them forth again at the beginning of a cycle.
Examples: ShishupAla, RAvana
All the above is applicable here.
Plus this state is during when the person is alive.
A person becomes free from the bondage in current life itself. It's also called "self realisation", where one realises Atma (the true self or the ultimate oneness).
In Gita, what is referred as GyAna -- is the enlightenment.
Among many verses, few are listed:
BG 4.39 - Faithful, Eager [and] controller of senses achieves Knowledge(Enlightenment); Achieving Knowledge, one quickly attains the ultimate bliss
BG 6.8 - Who is self satisfied with Knowledge and realisation, unmoved and victor of senses, is called absorbed [in yoga]; Such yogi treats soil, stone & gold equally
BG 7.18 - All of these, indeed, are noble, but Enlightened one (with Knowledge) is like My own Self in my opinion. Absorbed in self, that one is certainly situated towards Me as the best destination
BG 14.2 - By approaching this Knowledge(Enlightenment), My identity is attained; They neither born during creation, nor distressed during destruction
Examples: Lord RAma, Lord Krishna, Sage VyAsa
