No each awning manufacture makes their own annexes to fit their own awnings. Always check with a member of Davan caravans awning staff if you are unsure.
Yes, it is recommended that if you know their gales or storms expected then you should take your awning down. As any damage is not covered by manufactures warranty.
No each manufacture does their own straps to fit their awnings. If you are thinking of putting a strap that goes over the awning roof from one side to the other to hold your awning in position. Please note that if that strapping rubs on the roof and causes damage this will Not be covered under any awning manufacturer's warranty.