conform to/with // in conformance to/with // conformance/conformity
1. The proposal was written in conformance to/with the client's needs.
-Between "to and with", which is correct?

2. What's the difference between conformance and conformity? Are they the same?

3. The law does not conform to/with public opinion.
-Between "to and with", which is correct?

Question

conform to/with // in conformance to/with // conformance/conformity
1. The proposal was written in conformance to/with the client's needs.
-Between "to and with", which is correct?

2. What's the difference between conformance and conformity? Are they the same?

3. The law does not conform to/with public opinion.
-Between "to and with", which is correct?

Answer

Interesting question.  There is a useful discussion of it here : http://english.stackexchange.com/questions/77374/conformity-vs-conformance

I've only ever used and seen "conform to" (verb) and "in conformity with".  Both are formal.  The second one is especially formal.

"In conformance with" seems to be acceptable too but it would be useful to wait for other teachers to say if they actually use it, and if so, in which situations. The discussion I linked to suggests that "in conformance with" is appropriate for documents relating to standards.

I'd say that neither "in conformance with" nor "in conformity with" are technical in themselves, and they have the same meaning.  To me, it would be acceptable to use them interchangeably.