Manda is a snake and adheres to the venom a snake is capable of producing. The venom a snake is capable of producing has no effect on sand neither short term or long term. It will just be venom on sand until the venom dissipates.
And yes, all. You're trying to legitimize the situation by comparison, but Sasori was a puppet that could talk. All he had was a heart which was sealed. No brain, no lungs, nothing. The chakra did the rest. Puppets can be autonomous and work on their own, through chakra. Which is what the clan who made the tailed beasts specialize in. Some of the shinobi and tailed beasts can talk without their oral anatomy being able to really do so. Such as Katsuyu, Kakuzu when he releases his threaded tongue, so the point you are making are not good ones, in my honest opinion. There is also telepathy at play (in the series) as well as several other things so yes I believe Shukaku does all of that while simply being a construct of sand, no lungs, heart or anything of the sort.