Here's an answer from a British English perspective. American English usages are slightly different.
'Oven' refers ONLY to the closed compartment where you bake or roast things. You'd use an oven for baking bread, cakes, pies and tarts, or for roasting meat or poultry over a long period. Other types of ovens are open wood-fired pizza ovens, and microwave ovens. Generally, you put something in an oven, close the door, and then go away and let it cook.
'Stove' is less easy to define. At least in British English, 'stove' is actually quite an old-fashioned term for referring to kitchen appliances. (These days, when we talk about stoves, we mean enclosed wood-burning heaters for living areas). If I had to define 'stove' as something you'd find in the kitchen, I'd understand it as a synoynym of 'cooker' - in other words, a self-standing appliance which includes an oven, a grill* and a hob**. These are fairly unusual these days. When most people have kitchens fitted nowadays, you have an oven ( which includes a grill) and a separate hob at counter height which has several gas or electric burners.
A mixer mixes and a blender blends. Simple as that! You'd use a mixer, for example, for mixing together the ingredients for making a cake. Blenders are used to make lumpy things smooth - for example, you'd blend raw fruit and/or vegetables to make a smoothie, or blend cooked vegetables to make soup.
For any AmE speakers who are confused:
* grill: in this sense BrE 'grill' is the equivalent of 'broil' in AmE i.e. with the heat source above the food.
** hob: BrE equivalent of 'stovetop'.