Your chin rest, fingerboard, pegs and tailpiece are all made of ebony. It's absolutely fine to clean them with some kind of solvent, like vodka, white spirit or petrol lighter fluid, and every few months I clean my strings and fingerboard with lighter fluid to get rid of the rosin residue.
As rastaman said, put a duster down to protect the varnish! Just a single drop of solvent on the belly will probably make a permanent, devastating mark.
I don't think there's any need to loosen the strings, though. It destabilises the violin for nothing. It's fine to pull the strings slightly to one side to clean under them.
You can also clean your bow stick with vodka, but it's best just to wait until you have your bow rehaired because they will clean the stick at the same time.
Unfortunately, if there is rosin residue on the varnish, it is always best to leave it to the professionals to clean. My local string shop, Guivier in Central London, will do this readily - they have the correct fluids, which aren't commercially available - and they know which one to use for your type of varnish and how to use it.
The BEST way to keep your violin clean is to keep a duster in your case and to wipe all rosin off the belly, strings, fingerboard and bow stick every time you play. The horrid sticky rosin tide mark on the fingerboard will no longer form, and there won't be one on the belly either. The residue actually EATS AWAY at the varnish as long as it is left on. It'll still need professional cleaning every so often, but not nearly as often.
If you have a rash on your neck, consider a Strad Pad. They're quite expensive for what they are, but they'll save your neck! I nearly had a hole in my neck until I started using one, and now it's just a pink violin lovebite.
That is, if the rash is from abrasion. It could be an allergic reaction to the metal clamps, and a good solution to this is coating them with a little bit of clear nail varnish.
Hope that helps! Free of charge from another keen violinist.