Yes this is common after biometrics are completed.

No this shouldn’t result in a denial but possible RFE.

This should be from your most recently issued passport per form instructions.

Yes you will have to do a change of address and have the case transferred to local office, which may result in delays.

They should not be in the US for more than half a year on a tourist visa.

Yes you should be able to but contact NVC about next steps.

It may be best to submit a new I485 with appropriate I864 documentation.

Yes this is still possible but you must have some proof of valid entry.

Yes you may do so while the spousal case is pending.

You should wait until RFE is reissued to submit additional evidence.