you can store glass bottles on any shelf, the issue is the weight of the box, the rules for manual handling are to break down the contents to make the weight manageable, you can do this yourself, noone should need instruction on how to put a box or stock on a shelf if they have had the manual handling training.
cables are ok aslong as they are in a good state and not in a walk way or causing a trip or fall hazard. If they are then they need to be relocated or covered or a warning rign put up i would guess.
If you have a mobility issue then a letter rom your GP explaining that you are unable to carry out certain tasks is sufficient but no empoyer is forced to keep you in a job if there is a change in your capacity to do anm essential part of your job role.
Also in your induction you should have had the use of step ladder training for which you will have signed, your employer has a duty to maintain the safe condition of the ladders and it is also your responsibility to report any safety issues with the ladders and use them correctlt according to your training.
As for the boxes thing, I don't know what you mean.