These are technical questions, and you should seek legal advice if you’re going to take action or invest money.
“Retail services” (and “online retail services”) are listed in the class 35 IP Australia goods and services catalogue, so you can apply for registration of a mark which includes one or both of those specifications. The examiner may object to an “unrealistically broad specification,” but that is usually in terms of very lengthy specs, rather than broad individual terms, particularly if they’re already in the list. There are plenty of examples of registered marks which include “retail services” in cl.35.
An objection (or removal application) might be made on the basis that you did not use or intend to use the mark in respect of (all) the services applied for, or that the application was made in “bad faith.” The risk likely isn’t that you’d lose the whole registration (though you might for “bad faith”), but more that you might lose rights in respect of parts of the spec that you hadn’t actually used (eg, retailing of some specific product or category).
Hope that helps. Again, if you’re going to make an application, please seek some specific advice on these issues.