I have a couple of questions about house elves.

To free a house elf, you give them clothes. But house elves do all the work in the house. Does that mean that they can't wash the clothes from their masters without freeing themselves?

Also does the item of clothing have to be given to the house elf directly? Because in the books Hermione places her hand-made hats around the common room. The house elves of Hogwarts then refused to clean that common room because of the clothes. Does that mean that a house elf just has to pick up an item of clothing?

Also does the item of clothing have to belong to his master specifically, or could it just be any piece of clothing?

I personally don't understand how house elves became the personal slaves of wizards. I have perceived them as having magic that wizards themselves do not. For example they don't need a wand for specific types of magic. Also they can apparate to places wizards cannot (for example Hogwarts). I was always wondering that they, unlike goblins, centaurs or other magical creatures, even though they are magically quite powerful, allow themselves to be mis-used so much by wizards.

And a last thing I want to ask is if it is literately impossible for some magical reason, for them to dis-obey their master, or is it just their strong loyalty?

I hope all my questions make sense^^