Yes, it is possible, but it can be difficult for some women. Everyone’s anatomy is different, and the clitoris and g-spot can be reached anally for many women, but not everyone, or not as easily at least.
In many cases, women trying to reach anal only orgasms have found that it help to be very horny and not touch their vagina at all for days or even longer, with no vaginal orgasms at all and just lots of anal to keep trying. This can be hard to do, because when you get really horny you want to touch yourself and make yourself orgasm. Direct that feeling into anal stimulation instead and resist the urge to touch your vagina or clit.
This may take a while, and you may try it for a few days and then go back to vaginal and clitoral stimulation for a while, then try again. This is fine, and actually better for gradually building up the self control to do this.
Ultimately, I think it’s good to experiment with this sort of thing and see if you can do it, but if it ends up after a while of experimenting to be too hard or frustrating, then there’s certainly nothing wrong with enjoying anal penetration and clitoral/vaginal stimulation at the same time.