Learn Portuguese (Portugal): A colaboração entre as duas marcas é megaexclusiva, não é? - The collaboration between the two brands is mega-exclusive, isn't it?

When attaching a prefix ending in a vowel (like mega-) to a word starting with a different vowel (like exclusiva), the standard spelling rule is to combine them into one word. You only use a hyphen if the prefix ends in the same vowel that the base word starts with.

Does the prefix mega- change to agree with the feminine noun A colaboração?

The prefix itself never changes, but the base adjective it attaches to must still agree in gender and number. Because A colaboração is feminine, the adjective is exclusiva, making the combined word megaexclusiva. If the noun were masculine, it would be megaexclusivo.

Is megaexclusiva appropriate for all situations?

Prefixes like mega-, hiper-, and super- are highly productive in colloquial, everyday speech and marketing materials to express an absolute superlative. However, they sound too informal for formal writing or academic contexts, where you would instead use muito exclusiva or the suffix -íssima (exclusivíssima).

Can the tag não é? be used no matter what the main verb is?

Yes! While it directly matches the main verb é in this specific sentence, não é? (or its spoken contraction né?) acts as a universal question tag in Portuguese to ask for confirmation, much like "right?" in English. You can use it even if the main sentence uses a completely different verb.