Need some expert's opinions on how to rule out sentences such as the below

1. In Japan, unlike the United States, farms are small.

Is this form incorrect because we are saying "in Japan' .


2. In Japan, unlike in the United States,farms are small.


3.Unlike those in the United States,Japanese farms are small.

4. Unlike those in the United States, farms in Japan are small.

Need to know whether sentences 3 and 4 are the only correct ones in this list.

please help with detailed explanation (if possible) or similar examples.

What is the rule surrounding 'unlike' in the above cases?