Learn Portuguese (Portugal): A rua toda ficou inundada depois da tempestade. - The whole street was flooded after the storm.

This is the resultative passive. Using ficou focuses on the resulting state of the street after the event was over (it ended up flooded). If we used foi inundada, it would be the standard passive voice, which focuses on the action itself happening at that specific moment.

Does the past participle inundada always agree with the subject when used with ficar?

Yes. When forming the resultative passive with ficar (just like the regular passive with ser), the past participle acts like an adjective. It must agree in gender and number with the subject, which is why it takes the feminine singular form inundada to match a rua.

Is there a difference between saying a rua toda and toda a rua?

Both translate to 'the whole street', but placing toda after the noun (a rua toda) is extremely common in everyday spoken Portuguese to emphasize the street in its entirety. Putting it before the noun (toda a rua) is also perfectly correct but sounds slightly more formal.