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

No

While the spelling and the meaning of the plural noun "desculpas" (meaning "excuses") are identical in both dialects, there is a significant difference in typical usage regarding the act of apologizing. In Brazilian Portuguese, it is very common to use the plural form to express an apology (e.g., "Peço desculpas" — I apologize). In Continental Portuguese, the singular form is much more natural and standard for this purpose (e.g., "Peço desculpa" — I apologize).

Additionally, the pronunciation differs: in Brazil, the final "s" in "desculpas" is typically pronounced as an "s" or "z" sound, whereas in Portugal, it is pronounced as a "sh" sound.

Brazilian Portuguese

1. Não aceito suas desculpas. (I don't accept your excuses.)
2. Peço desculpas pelo atraso. (I apologize for the delay.)
3. Ele sempre tem desculpas para não estudar. (He always has excuses for not studying.)
4. Não venha com desculpas esfarrapadas! (Don't come with lame excuses!)
5. Peço desculpas pelo transtorno. (I apologize for the inconvenience.)

Continental Portuguese

1. Não aceito as tuas desculpas. (I don't accept your excuses.)
2. Peço desculpa pelo atraso. (I apologize for the delay.)
3. Ele tem sempre desculpas para não estudar. (He always has excuses for not studying.)
4. Não me venhas com desculpas esfarrapadas! (Don't come to me with lame excuses!)
5. Peço desculpa pelo incómodo. (I apologize for the inconvenience.)