Does India Army recruit soldiers whose native to highland region? Because it seems to me Indian Army is really good at mountain (high elevation) warfare. Hopefully they don't use / consume Diamox for acclimation (seriously bad long term health effect)
In addition to Gorkha already mentioned....there are these tough "local mountain folk" regiments (BTW "regiment" here refers to far larger mil org. rather than deployed field formation).
Some that pop to mind roughly going in arc of himalayas from west to east:
Ladakh scout, J&K Rifles, Garhwal rifles, Kumaon regt (highest decorated in IA), Dogra regiment, Gorkha regts, Sikkim scout, Arunachal/Assam regt, Naga regt.
They (locals) may also join other regiments of Indian army past the ones named after them...and other Indians may also join these named ones....but often the regiment recruitment is largely drawn from the local area its named after.
Other various Indian army regiments (Punjab, Bihar, Jat, Sikh, Rajput, Madras, Maratha etc) combine with these to form the larger brigades and divisions related to mountain warfare. They can also be deployed to regular terrain.
Officer Training basically is IMA (dehradun) which every infantry (officer) does...but where there is an extra Bhadraj mountain training.... and further than that is HAWS (high alt warfare school).
There are 13 mountain divisions (formed from these regiments and others too), 1 of them is fairly new (59th) and a mountain "strike" division .. with 1 more (72nd) supposedly in process of being raised in same way to eventually make a Mountain "strike" corps.
As
@Joe Shearer will tell you (along with any details I have forgot/erred upon), you dont want to really meet any of them mountain-folks/jungle folks in battle....and you especially don't want to meet the Naga (quite possibly, for your safety, even away from battle heh).