Sentence Correction

I wonder when S and V can separate remotely and when they should stick together.
EX)

OG says the following choice is wrong becase its verb should be are and it is too far from its subject

TV programs developed in conjunction with the marketing of toys, a practice that federal regulations once prohibited, is

But, following answer choice in another question is correct

The life of chekhov, unlike the lives of the subjects of other Troyat biographies, Pushkin, Gogol, Tolstoi, and Dostoevski, belongs

Obviously, the distance btw the subject, The life~, and its verb, belongs, are so long.


Admittedly, I should compare choices and focus on what the question asking for. But, I want to know the absolute rule of this issue. Do I just nee to think that "try to stick them together as possible as i can but if there is no choice like such, just take this issue as positive"?



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TV programs developed in conjunction with the marketing of toys, which was once prohibited by federal regulations, are thriving in the free market conditions permitted by the current

b) TV programs developed in conjunction with the marketing of toys, a practice that federal regulations once prohibited, is

This choice b is wrong but what if i change is to are?