Thank you for sharing your thought. I will answer only from Jain Dharma.

1) Is “Veer gati” mentioned in Jainism?

• In Jain philosophy there are four gatis (destinies): dev (heavenly beings), manuṣya (human), tiryañc (animals/plants), and narak (hell). “Veer gati” (a heroic afterlife due to dying in battle) is not a Jain category of gati. What determines one’s next birth is the type of karma bound by one’s inner passions (kashāyas) and intentions (bhāva), not a “heroic” death in war.
• The highest Jain ideal of “vīrata” (heroism) is inner victory over anger, pride, deceit and greed, culminating in vītarāgatā (freedom from passions). The noblest death in Jain Dharma is samādhi-maraṇa/pāṇḍita-maraṇa (e.g., sallekhanā), not death in killing or being killed.

2) Is being a soldier acceptable in Jainism?

• For monks and nuns: absolutely not. Total ahiṃsā is mandatory.
• For householders (śrāvakas/śrāvikās): Jain śāstras recognize that some limited, unavoidable violence (ārambhī-himsā) occurs in worldly life. Protecting innocents and maintaining order can fall under this sphere for kṣatriyas and state duty. However:

- Violence, even for protection, still binds karma. It is never spiritually “good”; at best it is the lesser evil when no non‑violent option exists. - Intention matters: acting without hatred, cruelty, or vengeance lessens karmic bondage; acting with passions greatly increases it. - Strict limits apply: avoid unnecessary harm; do not delight in killing; prefer restraint, de‑escalation, and non‑violent means; practice repentance (pratikramaṇ), alochanā, and atonement; cultivate dayā (compassion) for all beings.

3) About “martyrdom for the nation”

• Jain Dharma does not glorify dying in battle as a special spiritual attainment or a guaranteed higher rebirth. One’s future state depends on the purity of mind at the moment of death and the life’s intentions, not on patriotic sacrifice itself.
• True Jain heroism is protecting life while steadily reducing one’s own passions and violence. If one must serve, the path of least harm, strict self‑restraint, and constant purification is essential. The supreme path, however, is non‑violence in thought, word, and deed.

In short: Jainism honors protection of innocents but never celebrates killing. There is no “veer gati” category in Jain doctrine; the spiritual ideal is ahimsa and passionlessness, with samādhi‑maraṇa as the highest end.