I can answer the dress code bit.....very relaxed ...John took blazer and trousers with shirt and tie for 'formal' nights (which were more like smart casual ) there were alot of men in open neck short sleeve shirts!!! I wore evening trousers and glittery tops most nights. Our European cousins (who were the majority) don't seem to do formal!!!
we did ships excursions at all ports of call except Muscat where we were well and truly ripped off by a taxi driver who, in spite of us agreeing a price and route, disregarded both and we ended up driving up and down a dual carriageway and then through all the back streets to arrive back at the ship and he wanted double the price we agreed. So beware!!!!!
We sailed on the Classica in January and prebooked tours in Muscat (www.arabian adventures) and had an excellent tour with a young local gentleman. The itinery was similar to one offered by Costa but visited some extra places that were not accesible by coach and it wasn't as expensive.It also included soft drinks. In Dubai we booked a 4x4 desert safari with sunflower tours in Dubai. Again cheaper than Costa. In Muscat we were met at the Port Gate and in Dubai at the Cruise Terminal. They do other tours so it is worth checking out the websites and dropping tham an e-mail.
There were 2 formal nights and dressed was very mixed. The other evenings it was smart casual.