Is the word começou the same in Brazilian and European Portuguese?

Yes

The word "começou" is identical in meaning, grammar, spelling, and usage in both Brazilian and Continental Portuguese. The only difference lies in pronunciation.

In Brazilian Portuguese, the vowels tend to be more "open" and clearly articulated. In Continental Portuguese, there is a significant tendency toward vowel reduction, where unstressed vowels (like the "e" in começou) are often "closed" or almost swallowed, making the word sound more clipped or compressed to a Brazilian ear.

Brazilian Portuguese Examples

1. A aula começou tarde. (The class started late.)
2. O filme começou agora. (The movie started just now.)
3. Ele começou a treinar ontem. (He started training yesterday.)
4. A festa começou muito bem. (The party started very well.)
5. Tudo começou com um susto. (Everything started with a scare.)

Continental Portuguese Examples

1. A aula começou com atraso. (The class started with a delay.)
2. O filme começou há pouco. (The movie started a little while ago.)
3. Ele começou a treinar ontem. (He started training yesterday.)
4. A festa começou de forma excelente. (The party started in an excellent way.)
5. Tudo começou por um susto. (Everything started because of a scare.)