I was a previous crime scene investigator and biology/DNA expert.
1. There are chemicals other than the one you mentioned that will detect blood. No household chemicals can be used. Even the ones that we do use only presume that there is blood, further testing must be done. It would be difficult or impossible for a lay person to test for. A chemist could come up with something, or perhaps somebody could have read something, but a lay person with no specific knowledge could not.
2. Yes it would bubble, but just about anything in hydrogen peroxide will cause it to bubble.
3. Yes they give off heat during decomposition, not sure about the temperature. They would melt a little snow, not much. The cool outside temp would whisk away the heat almost immediately. The body would freeze and more likely be preserved rather than melt slow, the decomposition would be slow so the temp would really not rise.
4. Chemistry is used daily at crime scenes, so yes it is used. They are all neat tricks. Chemistry and physics are used in all of the analysis of samples, from trace evidence to DNA to drugs. Most of these use sophisticated machines to detect exact amount. Shelock Holmes uses neat tricks, but in reality we don't use them in a crime lab.
mmiller@forensicdnaexperts.com