I would say best to avoid them unless you define them separately and then continue using. Again the more common ones like etc, eg, are fine to my mind. Good luck
I would say it depends on the subject you are sitting. If its CA3 then you may get penalised. For example, if you have to use ie, this could mean you haven't expressed yourself properly in the first place. With other subjects, best define them once (unless they are good to you and give you both in the qn). Careful with etc. It would not be appropriate in a list question that asked for a specific number of points. If you have marking, maybe you will get advice on your scripts about these type of things.
