you want to shoot sunrise sunset at f2.8? that is very interesting,
and you want to shoot star trail at hotel balcony? that is very interesting too, for what I know people will go to remote places like desert or wilderness to shoot star trails.
hmm...are you saying... if u have a 24 F1.2 prime for eg.. you going to shoot at 1.2? is that why u asked for a prime lens in your first post? hmm..cool..i wont use such wide aperture tho. I dontknow what u can get from your balcony..but usually...isnt it better to go some wide empty area for stars? hmm..
Erm. Please do consider reading up on the basics. In fact, you can even test this on your camera. Switch to Av mode, set the aperture to 2.8 and look at the shutter speed. Now set it to 11 - look at the shutter speed. Notice anything?
FYI, people who shoot star trails travel faaaaaar to get away from all lights. I mean, middle of the desert, on top of mountains, etc. If you are shooting from a hotel balcony, I'm 99% sure you will have too much light pollution. You'll need to have a clear sky use bulb mode, shoot several shots up to 20-30minutes each, then consider stacking software, etc....
If you want to do star trails nearer to spore, go to some isolated dark beaches with no lights up north or stay on a kelong far out at sea and point cam away from the kelong lights... your best chance and Good Luck. Cameroon most unlikely.
If you've ever at some far out in the "wild" and look at some "distant city" you will see a canopy of light halo overhanging the city.