Mixed up about mixing plumbing pipe types

[themolene]

Nervous new homeowner trying to make sense on if this is all okay! I remember home inspectors calling out improper connecting of different pipe types, and we are doing some modifications, which means combining mostly old cast iron with new ABS. But looks like some older renovations also had galvanized steel(?). Is this all okay to combine like this, or should I just replace all the galvanized steel with ABS or cast iron?

If it matters, the steel looking pipes are vent only.

Appreciate any insight