Verse-3, Brahma Aksaram Paramam; here it means unconditioned one alone, and not conditioned one,which is indestructible,that which is all pervading.That which is free from all limiting adjuncts,which is the ruler of every thing,which is support of all including unlimited space,which is the Knower of the body and organs and is the absolute Consciousness. This very fact is explained by the word Paramam,Supreme.Paramam means that which is self- effulgent supreme bliss by nature.
Aksar also refers to syllable pranava(Om),but this is not accepted here because of use of word Paramam which is inapplicable to it(Om).
2, What is Adhyatmam-that which exists in individual body.
Svabhavah adhyatmam ucchyate;Brahman,s Nature and does not belongs to Brahman, it is our own self, Jeevatma,Consciousness w.r.to upadhi.
3, Visargah Karma,the vedic rituals themselves, consisting of yaga, dana and homa are called here Karma
Bhut bhavah udbhavkarah is Visargah. the offering,yaga,dana,homa that brings about the birth and growth of things is here termed action.
Yaga means parting with a thing in honour of some god;offering an oblation, in a standing posture,chanting mantrs vasat. that Yaga itself is called Homa when offered in a sitting posture ,chantig mantra svadha.Giving of gifts is called Dana. In all these three cases an element 'Giving up' is common.That it becomes the cause of birth and growth has authority of Smriti,
When an oblation is properly poured into fire it reaches to Sun,from the Sun comes the rain,from rain food, from food the creatures(Ma.Sm.,3.76) as also of the Sruti when these oblations are offered,they go up.(Sa. Br., 22.214.171.124),