How to differ a glycosidic bond and an ester bond?

I am studying this at a-level at the moment.
You will have to find out what the 'organic compound' is first by doing a variety of different tests, like the starch test. If it becomes positive then you know it is a starch product and has glycosidic bonds.
If it comes up negative you will have to do the test for lipids, and if that is positive then it could be a fatty acid and glycerol like you said and therefore would be an ester bond.
There is no point in working out what bond is involved if you don't know what substance or solution it is.

Biochemical tests will show this such as test for reducing sugars, starch and lipids, you would have to go on the positive and/or negative results of the testing