^ "try" to move your player first before using them keys...
ps: be aware that teleport/freecam can be tricky at times: basically you might get catapult-ed into the sky
. if that happens, either just wait until back "on your feet" (after disabling freecam), or try to FT (if possible)
(make sure to enable god mode AND check Readme suggestions for these features !)
btw: no guarantee that this will actually finish the mission; some values might/need to have been set prior to entering the cave (and whatnot).
if all fails, just post/pm your current location coordinates (xval, ...) and i'll try to get the exact coordinates inside the cave; which would then allow you to teleport to it...
as for "finishing a mission": i had a look at that in one of the other ac titles once; way too much happening here, apart from setting a flag or two... perhaps via calling the proper function (if one happens to know that one...)