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

Yes

The spelling, meaning, and grammatical function of "lindíssimo" are identical in both Brazilian and Continental Portuguese. The only difference lies in pronunciation:

• Brazilian Portuguese: The pronunciation is more "syllable-timed," meaning the syllables have a more even rhythm. The vowels are generally more open and clearly articulated.
• Continental Portuguese: The pronunciation is more "stress-timed." This leads to "vowel reduction," where unstressed vowels (like the first "i" in lindíssimo) are shortened or "swallowed," making the word sound more clipped or staccato.

Brazilian Portuguese Examples

1. Esse vestido é lindíssimo! (This dress is gorgeous!)
2. O pôr do sol estava lindíssimo hoje. (The sunset was extremely beautiful today.)
3. Que quarto lindíssimo você tem! (What a gorgeous room you have!)
4. O bebê é lindíssimo. (The baby is gorgeous.)
5. Esse carro é lindíssimo! (This car is gorgeous!)

Continental Portuguese Examples

1. Este vestido está lindíssimo! (This dress looks gorgeous!)
2. O pôr do sol estava lindíssimo hoje. (The sunset was extremely beautiful today.)
3. Que quarto lindíssimo tens tu! (What a gorgeous room you have!)
4. Áquele bebé é lindíssimo. (That baby is gorgeous.)
5. Este carro é lindíssimo! (This car is gorgeous!)