It is well known that laws & customs change over time, according to people, society and events.
Some people claim that religious scriptures also change over time.
But the wise say that religious scriptures do not change, but they already take into account all possible changes (combinations of people/society/events for all yugas) and codify those laws at the beginning.
For e.g. If a law states:
-  Stop on Red light.
Then in 2016, it gets amended to:
-  Stop on Red light, except if you hear ambulance, in which case, give way.
Then in 2017, it gets amended further to:
-  Stop on Red light, except if you hear ambulance, in which case, give way, but only if ambulance driver is within 20 ft of you.
In above case we can say 'The law changes over time'.
But if a law says:
- Stop on Red light, except if you hear ambulance, in which case, give way, but only if ambulance driver is within 20 ft of you, and if he honks twice to indicate you to move, (and other possible combinations)
In above case we can say 'The law does not change over time. It accounts for all possible changes ahead of time'.
Do scriptures fall under first or second category ?
If second, is there a different Smriti to be followed in each Yuga ?
If different, is there a hierarchy or gradation of rules, going from strict to relaxed from Krita to Kali ?
If gradation, is it because the scriptures/rishis are 'outdated', or because the society/people become 'degraded' ?
If latter, then is it acceptable for someone to follow rules of a previous Yuga ? For e.g. Crossing seas is banned in Kali but not in previous Yugas. Same with Niyoga.
If above unacceptable, is it acceptable to ridicule others for following customs of their current relaxed/degraded Yuga instead of a strict/exalted previous Yuga's rules ?
If above unacceptable, is the opposite OK - is it acceptable to ridicule others for following customs of a strict/exalted previous Yuga instead of their current relaxed/degraded Yuga's rules ?
e.g. people of Treta Yuga might ridicule those of Krita Yuga for always being engaged in Dhyana. While those in Krita Yuga might ridicule future inhabitants of Treta Yuga for always being engaged in Yagna.
Similarly, people of Kali Yuga might ridicule those of Dwapara Yuga for engaging in child marriage, being faithful/virgin, following varna separation etc. While those in Dwapara Yuga might ridicule future inhabitants of Kali Yuga for late marriages, multiple-sexual partners, varna-sankara (caste-mixing) etc.
When "social reformers" bring changes to constitutional laws (inherently according to scripturally mandated amendments for each Yuga), should they do so by deriding old scriptures, or by deriding new people?
e.g. When Sati/Child-marriage was banned long back, or when Adultery/Homosexuality was legalized recently, should it be done by stating :
'Old Scriptures are regressive/patriarchal/evil' ?
or by stating :
'New People are degraded/weak/animalistic' ?