On the third challenge, is it possible to bump, overfly the small building which has "The Bahamas" written on it and land on the building beyond it ? I think it's the hospital but I'm not really familiar with the city so I might be wrong.
Nah, 'cause for one the run up sucks & considering how close that building is to the bump, it's only possible to land it (the bahamas building) with a bump that has minimum distance, otherwise you'd crash into the house before getting the right height for it.
I've done it with a double-bump tho, with a different angle than what I imagine you've imagined