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

Yes

The word "achou" is identical in meaning, grammar, spelling, and fundamental usage in both Brazilian and Continental Portuguese. It is the third-person singular of the verb achar in the pretérito perfeito do indicativo (simple past). The only difference is pronunciation: Brazilian Portuguese tends to pronounce vowels more openly and follows a syllable-timed rhythm, whereas Continental Portuguese features more vowel reduction (making unstressed syllables shorter or "hidden") and a stress-timed rhythm.

Brazilian Portuguese Examples:

1. Ele achou a chave debaixo da cama. (He found the key under the bed.)
2. Você achou que o filme era legal? (Did you think the movie was cool?)
3. Ela achou o presente muito lindo. (She thought the gift was very beautiful.)
4. O cachorro achou o osso. (The dog found the bone.)
5. Ele achou que ia ser fácil. (He thought it was going to be easy.)

Continental Portuguese Examples:

1. Ele encontrou a chave debaixo da cama. (He found the key under the bed.)
2. Achaste que o filme era giro? (Did you think the movie was cool?)
3. Ela achou o presente muito bonito. (She thought the gift was very beautiful.)
4. O cão encontrou o osso. (The dog found the bone.)
5. Ele pensou que ia ser fácil. (He thought it was going to be easy.)