The shelf life of general purpose cement is 91 days. You can see how long it has been there before you buy by looking on the packing.
You can use sharp sand that has larger grains as this is good for laying paving slabs. You can also use soft sand as is better for bricklaying.
Sand is the most popular aggregate used but you can also use gravel, crushed stone or old pieces of concrete. If you do not use an aggregate you will end up with a product that will eventually crumble.
General purpose cement can be used for a lot of things ranging from small DIY jobs to large scale projects.