Magnum:
Often, in day-to-day conversation, we use expressions that may, or may not, carry over into formal writing. Informally, one says "this thing is different than that thing." Across the ponds, folk say "different to." In formal usage, it's "different from." Re: "enamored," it's always "enamored of," not with.
As to the preposition following "opinion," one can use "about," "on," "concerning," "of." However, in reference to beliefs or ideas, one might use "on": What is your opinion on my former cult?"
With reference to feelings, attitudes, behavior, etc., use "of": My opinion of his conduct at school is pretty low.
Last: I really have no opinion about financial matters beyond my own overdrawn bank account."
It's all about usage: what once was frowned upon has, in many cases, become standard. Take what you want and leave the rest . . .