Answer:
The answer is the sentence N. 4: Coding is computer programming that, when studied at a young age, can lead to future benefits.
Step-by-step explanation:
The chosen sentence doesn't limit itself to the types of benefits coding can give, like the others, that emphasizes on the benefit of gaining more experience than their peers (sentence 1) and achieving goals more quickly (sentence 3); and it doesn't present coding as one of the advantageous skills derived from working with computers. Instead, it focuses on the coding itself and their future benefits, in a general way, which allows the author to explore and give more detailed information about what those future benefits might be in a more extended way.
In the same way, the sentence is a perfect topic sentence since it is precise, has a relation with the thesis, and tells the reader what to expect from the following paragraph.