Can I use adult trees as supports when building a cabin?

Yes, but only make a firm anchor to one tree. Make sure the other anchors can slide. Otherwise the movement of the trees will rip your cabin apart.

Definitely. A lot of depends  on the atmosphere. If it’s cold you’ll have get your foundation down believe the frost line. 

The trees can support a TEMPORARY shelter. They CANNOT be used to support a permanent structure. Anything not freestanding IS NOT a cabin.

As Karen says, trees move, both in growing and with the wind and weather. In fact one next door fell down yesterday in the gales we were having. If that doesn't bother you and it's a simple shelter you could repair or replace easily then go ahead. Assuming you don't need permission.

Well, sure, it's possible to do that. Only thing is, trees grow. They also get old and die, or get blown down by wind. They also move when the wind blows. If you attach a place to trees, you may have to build it again or repair it in a few years. And if you have to get a building permit for what you're building, forget about attaching it to trees.

i would find out first if its legal to do that