Annie's hatch I'll leave to RFCC - it was an unpressurised compartment well aft on the port side of the fuselage and gave access to various bits of equipment that crew chiefs understood - all I know is it was handy for putting all your kit in when going overseas!
Annie's hatch, a.k.a. the Back Hatch / No4 Freight Bay. Used for carrying spare brake 'chutes, spares, APs etc.
.....the Green Satin was unreliable over water. On those occasions the crew chief must have slid his seat well forward to allow access to the periscopic sextant but I just can't picture it?
I only recall the perscopic sextant being used about twice, and then the crew chief swapped seats with the Nav rad. During Op Corporate Omega was fitted to the fleet, presumably the sextant wasn't required after that.