What will be my i94 expiry date on reentry with new visa?

You should be admitted for the duration of the petition and your visa should be issued for the same length of time.

H1b was approved but without i94 . Employer forgot to mark change of status option in the application .

If they timely apply for change of status, you should be allowed to change status. I think it is much better to travel abroad and get a visa and...

I agree with Mr. Segal. A police officer, even experienced would probably not be a suitable occupation for H1B visa purposes.

How long is the process for an Italian to be able to come to America to work?

Are you being sponsored by anyone for work for family in order to come here?

You will be able to change this information during the interview.

I got marry while im with tourist visa do i need to ask for an extension of my visa or can i just start legalization process?

Generally speaking, immediate relative's failure to maintain status is excused. You need not file for extension.

If the error was of the USCIS office, you should be able to.

Can an employer withdraw an H1B petition when RFE is issued?

The last employer approved as your employer is going to be your employer.

Can I open a small physical shop with L1-B VISA and have my wife who holds L2 VISA (no EAD) to sell goods there?

No but she could be the owner of that shop and also work there once she got her EAD.

I am also confused as to the gist of your question.