It is old English slang. It was used a lot the word snag in the 80s. You could snag a deal or bargain or even snag yourself a good looking partner etc. I don't hear it these days.

Yes, in the United States is a common, correct, but informal usage. My personal favorite dictionary is the American Heritage because it has very clear definitions, and, on some words, excellent usage notes. For "snag," it gives three meanings as a noun, and four as a verb. The one you want is: "_Informal_ To catch or obtain quickly or unexpectedly: _snagged a ground ball;_ _snagged a bargain._ Depending on where you got the text, though, it is possible that it might be a misprint or OCR scanning error, for "snap." "If we can snap a photo of it..."

I’ve never heard “snag” a photo but when I read it I knew exactly what it meant in context. I wouldn’t say it’s wrong, it’s just not common. This would sound more natural: “If we can get a photo of it” 🌈

FWIW I agree that "snag a photo" sounds a little unusual, but on google, "snag a photo" has 525k hits, "snag a picture" has 402k hits, and "snag a shot" has 908k hits. There is also a software app for taking screenshots called SnagIt (which I've used a lot over the years). So maybe it's not that unusual.

Yes, it’s good.