You cannot
The only official "secret areas" are the Lairs of Romulus, which you can complete to unlock the Armour of Brutus and the Dagger of Brutus.
Through a system of trial and error, if you're skilled and determined, you could get through Assassin's Creed: Brotherhood without purchasing any armour upgrades.
Some of these are found and others are bought online: Assassin robes Armour of Brutus Ezio in the Monteriggioni attack Raiden skin Online: Armour of Altair Altair's robes Ezio Florentine Noble atire
yes you can. in fact i did myself cause i wanted to see how it ended so after i beat the game i went to the romulus lairs and beat them and got the armour of brutus.
You are unable to join them, but you can wear their armour. :)
coz its there armour and assassins wear
You unlock the Desmond PC (playable character) by achieving 100% synchronization on DNA Sequence 8 ("The Borgias"). Not that the Desmond PC is simply cosmetic - you will still retain all of Ezio's armour and weapons.
You need to find the armour of Romulus which you get for finding all the keys in the Secret Locations missions in the DNA menu then using them to unlock the gates underground where the armour is. This is where the gates are and what happens when they're unlocked.
You can't. The Armour of Altair isn't available until AC2.
THe armour of Brutus has actual stats, while Altair's is purely cosmetic and will take on the stats of whatever armour you're really wearing.
You have to find the keys that are scattered around The Tombs of Romulus. It easy to get.
Unfortunately not, only normal armour can be dyed. If you want coloured armour just go into your villa and change into a different set then go to tailor!