Taja is a language with Verb-Subject-Object word order. However, emperor Kai wants to always be the first, so, he wants all sentences where he is the subject to have a Subject-Verb-Object word order.
Obviously, people at the court follow this rule. Farmers in a remote region probably not that much. If Kai dies a few years later and his successor goes "Stop this stupid word-order thing" this would be forgotten quickly.
If, however, Kai lives long enough (or his successor also likes it this way), other nobles would start to require their servants to put them first as well, eventually even remote regions would pick it up. Finally, it becomes part of the language.
How long does this need to stay in effect until language development integrates it into the language? Such that even after replacing monarchy with democracy, the "Subject-Verb-Object" word order is still used when the subject is a person, and the speaker wants to express his/her respect?
Let me answer the questions in the comments.
First of all, Kai is not planning to systematically change the language. He is just pleasing his ego. So while he will punish people who do not do it (if he notices), he is not going to start a large-scale education program.
If the emperor is the object of the sentence, the sentence stays as it is. So "peasants must pay taxes to the emperor" stays unchanged.
What is the equivalent Earth date for technology?
agricultural, probably medieval.
How physically and demographically large is the country?
An entire continent. Think about the Roman Empire.
How much trade is there with other countries?
I haven't given this one any thought. I guess less trade helps, so, let' say very little.
How strong is/are the religious influences (a big deal with language)?
weak to medium
How effective is the collection of taxes and the dispensation of justice?
Things are quite organized, however, this is a personal spleen of Kai. A judge (or policemen) in a remote province is very unlikely to sentence/imprison someone for not following this.