Word choice help

What do you mean by the 'at'-mark?

the @ mark is the name/account of that person (@janemiller is the person who took the pic). I hope I have managed to clarify.

Well the standard credit is 'photo courtesy of @Janemiller'.

Thanks. Any other option that would work. Would 'by' or 'from' work? And what would 'via' mean, as I have seen some use it but don't quite see the reason behind its use.

Does 'via' mean: the picture reached me by way of/through my friend?

Would you please tell me which of the rest would work, even if not as good as 'courtesy of?

Dear teacher, would you please answer my last questions regarding the subject.

Please use the one I have given you.

Dear teacher, I have used it already, but would like to know how to use the other ones and If I have understood them correctly by my explanation of them to you?

Yours in the first post do not seem native.

Got it, and thanks for giving me the best. But I would just like to know what would 'via' mean. Could it mean that I received that photo from this person?

Does 'courtesy of' mean thanks to this person who took the pic?