1. "Realistic" in this situation suggests that the plan is being made more like "real life" or how things normally happen. "Practical" suggests that its easier to do. But really, they can both mean the same thing, and are techincally interchangable. "Realistic" reads better though.
2. Your interpretation is correct. And in your sentence, you could replace "periodical" with "cyclic", we often talk about the "cyclic" nature of economic models.
3. You can use "on". Personally, I would use neither and use "to" instead.
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