comma after 'about'/before 'and' [preposition; serial c.]: are about,

[quantum zero]

Here is what I wrote "I researched what the companies are about, what they do and what I would be working for if I became a part of this companies." If you could read my sentence I would like to ask two questions. I put comma after 'about' and is that appropriate or not? And I wrote 'and' between 'do' and 'what', is it grammatically correct?

Thanks

 

[Keith Bradford]

After about, the comma is absolutely necessary.
After do, the comma could be omitted, but I feel helps to make the meaning clear.

 

[Copyright]

And if you would like an AE opinion, I agree with Keith -- I would use both myself: I researched what the companies are about, what they do, and what I would be working for ...

"What I would be working for" is rather odd, by the way. It sounds like you want to know what sort of salary or medals or rewards you'd be working for. In AE, "what am I working for" can also mean "why am I working."