Basement through block wiring?

I have an older house, 1960, in which the basement was wired from the start and all the lines run down through the block cavities. The boxes, metal, are mounted into holes drilled/chiseled out of the block, this includes switches and receptacles.

I assume that was fine per code back in 1960....now, I'm betting it's so far from code it's a borderline fine, LOL.

If I were to replace anything that's current and existing - switches/receptacles, I could do so the same way it's run now?

If I were to add an additional switch/outlet/circuit, either DIY or through an electrician, would only the new items need to be to code, or would the entire basement circuit(s) need to be brought up to code?

Thanks