No, a sphere pertains to three dimensions. A three dimensional item always contains a two-dimensional "round" description. Not vice versa.
The context of use means everything.
No, the context is merely that which you decide to "read into" it, your personal "eisegesis". I'm not sure what the babble above means. What I said is that the word "rotundus" in Latin done not necessarily mean a sphere, but could be something two-dimensional. St. Thomas simply uses the Latin "rotundus", which globers claim refers to a sphere, but that's not necessarily true, and there's no "context" in the citation above that requires that it be read as a "sphere" other than your own wishful thinking and confirmation bias, where you imagine that he used a word that means "sphere", which he did not.
No one has yet provided a citation of the Latin for the Commentary on Aristotle that someone translated as "sphere".