"Are this given group a Christian group?"
"Is John Doe a Christian?"
This is a divisive question. Any questions that attempt to divide Christians into groups will be Not Constructive, since it will garner answers that say "Yes" and "No" (and inbetween). The answers will turn into a vote war and a debate. Because of this, questions regarding whether a specific group is Christian is Not Constructive for this site. See the FAQ for the definition of "Christian"
"Is it a sin to do drink alcohol?"
"Is it a sin to get a tattoo?"
These types of questions are not constructive because they do not specify a doctrine or doctrinal tradition (eg denomination). Since these questions don't specify a doctrine/tradition, they are unfocused and will gain several answers from different traditions. Most of these answers have historically turned into pure speculation and opinion. Because of that, these questions are Not Constructive for this site.
"What does John 7:11 mean?"
"What does John mean in Revelation 21?"
This is only off topic when it does not specify a doctrine or doctrinal tradition (eg denomination). Interpretation of text (exegesis) is always done from a doctrinal viewpoint. If you are seeking the understanding of text without specifying a doctrine, then the answers become a free-for-all, garnering all viewpoints. Historically, we've seen that this primarily gathers opinion and speculation, which is not constructive for this site.
"Is 'murder' a good translation of the word in Deuteronomy 5:17?"
This question is asking for a translation from the original Hebrew. Questions like this aren't really on topic for this site. They should be directed to BiblicalHermeneutics.SE instead.
"How should I deal with this situation?"
This type of question is known as "pastoral advice" questions. These questions are very specific to your circumstances and, therefore, are too localized for the internet in general. The answers won't be useful to other people. Furthermore, it's impossible (in this format) to gain all the details necessary to truly help you in a given situation. For help with this type of problem, you really need to seek advice from your local clergy or lay counselor.
"Where can I find useful resources on this subject?"
"Can you recommend a good church in this city/area?"
This type of question can result in numerous answers that are all (arguably) correct, resulting in a list that could potentially be added to indefinitely. In addition, what one person finds "good" or "useful" another person may not. As such it would be difficult or impossible to provide a definitive, objective answer to such a question.
"What should Christians think about this concept from another religion?"
"Was this Christian belief originally a belief from another religion?"
Like many topics, this line of questioning is purely speculative and potentially divisive. Christianity, as a religion, doesn't deal with concepts from other religions; it deals with concepts from Christianity. This line of questioning is really more of a philosophy or sociology question and doesn't really belong here, since it's not constructive for this site.