Peace kaamil.
You say ,quote:
"The biggest question that bother my mind is that if God is All knowing, wouldn't He He know that all the knowledge and development will evolve as at now, or is it that quran is discussion a completely different topic and we are mistaken it for iddah?"
It is a different topic .Pregnancy or having children already are irrelevant here .A widow has no restrictions or ties to another man. It is a pre-marital interim . I believe it is time to grieve,, reflect and get back to some kind of normality . There may be engagement or getting to know the new partner , but marriage can wait for this required interim . GOD confirms for us in the verse that He has full knowledge of everything we do at all times:
"
Those who die and leave wives, their widows shall wait four months and ten days (before they remarry). Once they fulfill their interim, you commit no error by letting them do whatever righteous matters they wish to do. God is fully Cognizant of everything you do."
GOD bless you.
Peace.