Qasar Salaah and Full Salaah

Q: I live in Morocco but i own a holiday flat in Portugal which stays empty most of the year, when I go there am i musaafir?

 Q: If a traveller leaves his home for the airport (approx. 25 km away). At the airport, will he have to read qasr salaah or full?

Q: If a person on safr performs salaah alone and intentionally performs full Salaah, will he be sinful?