No, it is not described as “mandatory to first bear or shed all nikachit karmas of all previous births” one by one before liberation. But some important clarifications are needed:

1. What is nikachit karma?

In Jain philosophy, karmas have different levels of firmness. One type is nikachit (निकाचित) karma – the “tightest / hardest” bondage. Key point:

• Nikachit karmas are those which, once bound, must give their result; they cannot be avoided or cancelled by ordinary effort. ( jainknowledge.com)

They can be:

• Pāpa (inauspicious) – e.g. severe suffering, death in a particular way
• Puṇya (auspicious) – e.g. certain fixed enjoyments

For nikachit, the general rule given in scriptures and commentaries is: > “They are destroyed only by giving their fruition.”

2. Then how does liberation happen?

Liberation (moksha) means all eight types of karmas are totally destroyed at the last moment of the final life.

This happens in two ways:

1. Through uday / udirṇā (fruition):

- Many karmas, including nikachit, have already given their result in various lives and are finished.

1. Through intense spiritual effort of the last life:

- By keval jñān and extremely pure meditation, the remaining karmas (including ghāti and aghāti karmas) are destroyed from the root so that no new bondage arises, and the balance is completely exhausted.

So at the moment of moksha, the soul is absolutely free from all karmas – nikachit and others. But that does not mean:

• “You must consciously go birth by birth and bear each past nikachit karma separately before you can become liberated.”

Rather:

• Whatever nikachit is still active and has not yet given effect,

- either ripens and gives its effect (even very fast, in the last life), - or is destroyed in that final intense state when all karmas are exhausted.

3. Is every bound nikachit karma of all past lives felt clearly?

Not in a way we can count or recognize. From a soul’s viewpoint in saṃsāra:

• Innumerable karmas (including nikachit) have already:

- arisen, - given their result, - and gone.

• What is presently in satta (dormant form) will:

- either arise as experience sometime, - or get destroyed in the final stage of purification.

Jain texts do not tell a layperson to worry, “Have I borne each and every nikachit karma from each previous birth?” They teach us to:

• Stop new bondage (saṃvar)
• Shed existing karmas (nirjarā) through:

- right faith, right knowledge, right conduct, - vows, austerities, meditation, etc. ( jainknowledge.com)

4. Do Digambar and Śvetāmbara differ here?

On this principle, both agree:

• Liberation = complete end of all karmas.
• Nikachit karmas are those that must give their effect once bound. ( jainknowledge.com)
• The path is the same Ratnatraya (right faith, knowledge, conduct).

Differences are mostly in:

• detailed classifications,
• emphasis on austerities,

but not on the basic rule of nikachit karma and moksha.

5. Simple, practical understanding

1. Yes – any nikachit karma that is still bound must, in some way, be concluded (by fruition / destruction) before or at the moment of moksha.
2. No – you do not have to “consciously suffer each one in full detail across countless births” as a precondition you can track.
3. Your focus should be:

- Reduce passions (anger, pride, deceit, greed). - Practice non‑violence, truth, self‑control, and non‑attachment. - Strengthen right faith, right knowledge, right conduct.

Through this, the stock of all karmas (including nikachit) becomes smaller and smaller, until in the last life they are completely finished and the soul becomes a Siddha.

You can read a simple explanation of karma levels (including nikachit) here