I am waiting on U visa. Applied on OCT 2014. Im working on OPT and want to apply H1 this year.

Yes you can, if your maintain your nonimmigrant status all the way to September 30, 2015 or you fall under the GAP CAP. I assumed your visa will be CAP subject, of course. Talk to the employer's lawyer.

Yes, an employer could petition you for an H-1B, but you will only be able to change status to H-1B in the US if previously maintained valid non-immigrant visa status. If you did not and will need to depart, you could then be subject to the 3 and/or 10 year inadmissibility bars.

AS long as you are in a valid nonimmigrant status on September 30, you can change to H1. Otherwise you will have to seek consulate processing on your H. U has nothing to do with any of it.