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

Yes

The word "opinar" has the same meaning, spelling, and grammatical function in both Brazilian and European Portuguese. The difference is strictly phonetic.

• Brazilian Portuguese: The pronunciation is characterized by more open vowels. Unstressed vowels are generally articulated clearly and distinctly.
• European Portuguese: The pronunciation involves significant vowel reduction. Unstressed vowels are often shortened, swallowed, or almost entirely suppressed, making the word sound much more "clipped" or "closed" to a Brazilian ear.

Brazilian Portuguese Examples

1. "Não venha opinar na minha vida!" (Don't come giving your opinion on my life!)
2. "Eu estou opinando sobre o novo projeto." (I am giving my opinion on the new project.)
3. "Ele gosta muito de opinar sobre tudo." (He likes to give his opinion on everything very much.)
4. "Você pode opinar sobre esse assunto?" (Can you give your opinion on this subject?)
5. "Ninguém me perguntou para opinar aqui." (Nobody asked me to give an opinion here.)

European Portuguese Examples

1. "Não me venhas opinar na minha vida!" (Don't come giving your opinion on my life!)
2. "Estou a opinar sobre o novo projeto." (I am giving my opinion on the new project.)
3. "Ele gosta muito de opinar sobre tudo." (He likes to give his opinion on everything very much.)
4. "Podes opinar sobre este assunto?" (Can you give your opinion on this subject?)
5. "Ninguém me pediu para opinar aqui." (Nobody asked me to give an opinion here.)