I hope that this thread can finally answer how exactly FE sun shines its light to create day on one part and night on the other part of a flat earth. I have heard one FE theory suggesting that the sun is spherical but somehow acts like a spotlight to explain why it looks round during the day and is not visible at night.
In RET, the Earth's rotation axis is tilted 23.5 degrees from the plane of its orbit around the sun which creates seasons while Earth is orbiting around the sun.

Below shows how Earth receives the sun's light on June and December solstices. in June, the northern hemisphere receives more sun light than the southern hemisphere creating summer time in the northern hemisphere and winter in the southern hemisphere. In December, it's the other way around. But regardless of the time of the year, one half of the spherical earth is in day time while the other half is in night time. Half earth is day and half earth is night. Half and half.

There are many sites that show day night map available on Internet. For example you can check what part of the world in in day time or and night time depending on the day of the year and the time of day in
http://www.timeanddate.com/worldclock/sunearth.htmlI tried to project day and night on a flat earth map depending on the month (March, June, September and December). The below sketches show the sun light (the yellow highlight) as perceived by a flat earth in function of the time of the year.

We can see than the shape of the sun light on earth is different depending on the month. In June, the sun is nearer to the north pole and shines in perfect circle on earth giving longer daytime to the northern part. This is probably what is referred to as "spotlight" by some FEers. But in March or September, the sun doesn't shine like a spotlight anymore. In December, it's getting worse. I cannot even find a word to describe how the sun can light the outermost of the disk while creating a dark spot in the middle.
Is this the death of the FE spotlight sun?
I used monopolar model for this work. When I get more time, I'll include the bipolar model too. I have the impression bipolar model will be even weirder than the monopolar one.