Can I substitute the synonym "refuse" to check if a sentence with the word "disdain" makes sense?

"The difference between the almost right word and the right word is really a large matter. It's the difference between the lightning bug and the lightning." (Mark Twain)

The connotations behind the two words in your usages could have a daylight of a difference between them.While there is nothing wrong with the sentences themselves (except that the full stop is conspicuously missing), the intended meaning could suffer for want of mot juste.

I would say the meaning has more to do with disapproval rather than refusal. I might disdain a new policy but not refuse to follow it. It can often carry a connotation of snootiness.

Disdain, the noun, is close to 'contempt' in meaning. So the verb naturally has the same connotation.

Refuse is broader - you can refuse to do or take something for many reasons, not just out of disdain. Conversely, you can "disdain" something, but it doesn't necessarily mean you refuse it.

To be honest, I'd avoid using it altogether in the verb sense. It's quite uncommon these days - I can't actually recall when I last saw it in prose. Many years, at least. If I saw it now, unless it was in a character's "voice", it'd give the impression (to me, at least) of someone reaching very hard for over-elaborate, "fancy" language.