Gassy Information

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In designing experiments it is important to be sure that the data measured will be sufficient to reach a desired conclusion. In each of the following situations, will the information provided always, sometimes or never be sufficient to determine the required information about the reactants? Provide a clear analysis in each case.
 

• A gaseous alcohol is completely combusted with an excess of oxygen at $400$K. The change in volume of gasses is measured. Can I determine the formula of the alcohol?
• A gaseous hydrocarbon is completely combusted with an excess of oxygen at $400$K. The change in volume of gasses is measured. The system is then cooled to $273$K and the change in volume of gasses measured. Can I determine the molecular formula of the hydrocarbon?
• A quantity of gas is contained in a piston which is configured to exert a fixed pressure on the gas. The volume of gas is measured at two different temperatures. Can I determine the number of moles of the gas present?
• A gaseous hydrocarbon with known molecular formula is combusted with an insufficient supply of oxygen, resulting in a mixture of H$_2$O, CO and CO$_2$, with no oxygen present. The initial volume of hydrocarbon gas and the change in total volume of gas are measured. Can I determine the initial volume of oxygen?