I'd be very cautious about it.

I wouldn't recommend it. But that is to your own discretion if you choose to do so but have a firm grip on it.

I don't see why not - Uma's base is quite large. I just wouldn't try to push the penetration too deep. If want deep penetration, you should look at other alternatives.

You can and I have. You just have to use extreme caution. The base isn't wide enough to stop being sucked. But it acts as if it's a handle. If you keep a hold of it it'll be safe.

I would really recommend against it, because the base ISN'T that much bigger than the insertable portion, in my opinion. If you were really into it, you might not realize that it was in a bit deeper than you wanted.

I would recommend it for anal use with a partner, though, because they'd be able to gauge when it was in deep enough as well as making sure they had a firm grasp, which you might not be able to do on your own.