There are major differences regarding capitalization rules between English and French, but the influence of English tends to make these rules very porous.
These are the rules to always be followed :
Always use capitalized accents: É, È, Â, Ê, Î, Ô, Û, Ä, Ë, Ï, Ö, Ü, À, Æ
Be consistent. Whether a specific guideline for the project has been provided or not, stay consistent with the rules as set.
Incorrect: Appuyer pour Collecter Toutes les Récompenses.
Correct: Appuyer pour collecter toutes les récompenses.
Incorrect: L'armée Athénienne est en retraite !
Correct: L'armée athénienne est en retraite !
Incorrect: L'événement de Noël est sur le point de commencer.
Correct: L'événement de Noël est sur le point de commencer.