Why kali yuga has to prevail? And Yuga determine us humans or we
Looking forward for others view and answer of this question, I will choose rather weird way to answer it.
In shri surya siddhanta, chapter 1: on mean motions of planets,
- Thine intent is known to me; I am gratified by thine austerities; I
will give the science upon which time is founded, the grand system of
It's pretty clear, the motion of the planets have been used to divide time into the yugas. Following the siddhanta go on explaining how time is represented for god, demons and Bhramha. The yugas are separated here:
- The tenth part of age (caturyuga) multiplied successively by four, three, two, one gives length of golden and other ages.
This shows us that however we view it, the yugas prevail as they occur due to planetary motion itself. But it also follows that the events that happen in each yuga are already predetermined. Why is that? Probably no one knows. So yugas are not determined by us, since the revolution is controlling it. Do yuga determine us, probably yes. Its pretty clear that yugas are not identical in first place, each consists of diffrent amounts of time. Satya yuga being the longest and kali to be smallest.
What happens if I chant Treta or krita yuga mantras during this very period of yuga?
I dont know or I dont think a mantra can be classified according to yugas. What about 'om', which yuga it comes from. Mantras must be classified according to their Gunas only.
But there are certain restrictions on 'yagnya', in Sarvollāsatantram,
अनुकल्पं कलौ देय॑ पशुमात्रं विशेषकम् ।
अश्वमेधं कलौ भद्रे द्रव्याभावे परित्यजेत् ॥ ११ ॥
It says the ashvamedh yagnya over the purpose of gaining 'dravya' must not be performed ( intact its restricted- 'varjit')
Are vedas to be read less...
Note that Different texts will encourage different things, from Sarvollāsatantram
अथ युगभेदे शास्त्राचरणम्--
सत्ये श्रुत्युक्तकर्माणि त्रेतायां स्मृतिसम्मतम् ।
द्वारे च॒ पुराणानि कलावागमसम्मतम् ॥
It says in satya yuga- karma as per vedas, in treta as per smriti, in dwapar as per purana, in kalikal as per Agamas.
Why it is not advised to perform other Yugas activities into a particular Yuga?
As @Rickross already has answered it, in kali yuga bull stands on one leg, bull barely can stand and Dharma falls apart in kali yuga. We always need change as per situation, and thus then our activities must differ.