Question about label and comments

Hi, everyone,

I wonder if there is any rule about using skos:note and rdfs:comment?
For anything that is general enough (e.g, not example, or definition, or
changeNote, etc), is there any restriction or drawback to use
rdfs:comment? 

I think rdfs:label falls into the same situation. If there is only one
label available for a class, should one use rdfs:label or
skos:prefLabel?

In addition,SKOS has changeNote and historyNote. We are not very clear
about the difference between them. For example, if I want to stay that I
added definitions to this ontology, should that be a changeNote, a
historyNote, or even an editorialNote?

We would really appreciate it if someone can give us some clarification
on these confusions.

Thanks,

Cui