Would the medicine risperidone block the effects of acetycholine in brain?

Not likely: Risperidone is a dopamine and serotonin blocker, and doesn't directly affect acetylcholine transmission. Studies in animals and humans have shown risperidone may increase acetylcholine activity in the cerebral cortex through indirect actions, and this may account for some of its positive clinical effects e.g. on cognition in schizophrenia.