can I get a loan for an rv as a (second home) mortgage instead of
applying as an rv loan. I know I can deduct the interest of the loan
as a second home, but can I also apply for the loan as for a second
vacation home and get a better rate?

I very much doubt it.  For your bank's purposes, I would think your RV
is much more like a car than a house.  If you default on your loan, it
is a lot easier to run off with or hide the RV than it is to run off
with a house.  Plus, a house will tend to appreciate, whereas an RV
will depreciate leaving less to recover in case of reposession.  That
said, banks seem to be passing out loans like candy these days, so
anything is possible.

No, you most definately cannot.

If you have sufficient equity in your home, you can look into
refinancing your house with a cash out refinancing.  The cash could be
used for quite a few different things.  But be up front about what you
want to do with the cash.  But bear in mind, if you default, it's your
home that is at risk, not the RV, since your home is the security for
the loan.  That's what you could do.  Whether it is a good idea is
another question.