Yes you can ask for a Succubi if you're only 14.
When doing the ritual be VERY VERY speciffic about your needs and
what type of relationship you wish to have with your Demoness lover.
For example state if it is just a sexual relationship and you both
are free to have other relationships with other people or if you plan
on being in a loving relationship where you are faithful to her and
her alone (you can make it so that she's the only Demon(ess) you have
relations with, but you're free when it comes to humans). Be very
speciffic if its an open or closed relationship.
As for the ritual I've read about a few way to do it, however what I
did was I meditated several times to Father about it and stated my
needs and all that fun stuff as well I performed a ritual where I
wrote a prayer and burnt it in the candle fire.
One thing I would like to point out is, you WILL need to work on your
ability to see and hear things on the astral plain. It can a while to
do such and I've heard about some one who is way more advanced than I
who still cannot fully see their lover. Hope this helps.