Forcément vs naturellement

Naturellement and forcément have slightly different historical/etymological meanings, but nowadays the difference is so small that most people will not make the difference.

In the 3 sentences you provided, both naturellement and forcément are acceptable, they work fine and the sentence means almost exactly the same.

If you really REALLY want to have a difference between both adjectives, it would be the following:

• forcément would be employed for an obligation that comes from a "higher authority", for instance the law, or your boss, or your parents if you are a child, or a logical reasoning. For instance: comme 1 est impair, le chiffre suivant est forcément pair ("as 1 is odd, the next number has to be even").

• naturellement would be employed if the obligation comes from "the nature", in the sense of something so evident that it does not need to be explained further. For instance: comme il fait très froid dehors, il va naturellement geler ("as it is very cold outside, it is going to freeze.")

So you can use both adjectives in the same sentences, and choose one or the other depending on whether you want to insist on a "natural obligation/consequence" or an "obligation coming from above".

Naturellement and forcément have different meanings. Naturellement is also more formal than forcément and is often at the beginning of a sentence.

It seems forcément would better fit most of your sentences, but they are all slightly odd.

Même s'il est triste, il essaye de continuer à vivre comme avant. Naturellement, il doit encore aller à l'école tous les jours.

Il a reçu un texto sur son portable et comme il est très curieux, il doit forcément le regarder tout de suite or (il ne peut pas s'empêcher de le regarder tout de suite.)

Il n'a jamais vu un truc pareil alors forcément, il prend tout de suite une photo.