1. When these three words are followed by nouns such as 法律、规定、经验、方案, they are interchangeable. Following the example u put up here "按照（依照、根据）学校的规定，你们每学期必须选修两门课", you are explaining or quoting what the school's rules say about registering for electives. No conclusions or implications are being drawn or made here. They're the equivalent of "according to" under this circumstance. 2. "依照" / "按照" 就是把A作为标准、照着A的要求做 - You do something following the rule/requiremnet/ order/ standard of A "根据" 就是把A作为基础，在这个基础上在做某市或得到某个结论 - It describes the relationship between the two statements of a conditional statement A, called the antecedent and B called the consequent when A implies B or statement B can be drawn based on A. 这部电视剧是根据古典小说 "红楼梦" 改编的: This sentence is emphasizing "to be based on" because 这部电视剧 is an adaption of 古典小说红楼梦。The show is not explaining 古典小说红楼梦 nor following the order/requirement/order of 红楼梦. 3. Furthermore, it says: 当后面所引人的是顺序、时间、期限、比例、范围等方面的次于是，多用"按照"、"依照"，不能用"根据". - This entry is oversimplifying. Again if you are trying to interpret or quote something (according to something), there is no such difference in usage. If it is following the order/rule/requirement of something, then 按照／依照would make more sense in the sentence。这篇文章是按照时间顺序协作的。（不可以用根据）－ The article follows a chronological order. 4. one book says 根据 is preferable while another says 按照 is: 根据/按照 天气预报，明天会下雨的。This one is a bit of tricky as both are acceptable in the context but I'd go with 根据 as u‘re quoting or interpreting the weather forecast。 Hope it helps!