The tree form of the Hydrangea will do fine in a container for a limited time. Maybe two or three years before it will need to be placed in ground. Almost all varieties of hydrangea will need extra protection in your area to grow outside.
Many of the smaller shrub forms and climbing forms can stay in container for extended periods with some maintenance.
This article will help: https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/hydrangea-container-care.htm
we a have new hydrangea tree just set out and the flowers are turning brown but the tree limbs are still healthy. Any suggetions on how to treat this issue? I have cut some of the brown blooms off but others are turning brown now.
If you've inspected your plant and it has no insect or other damage, the browning of the blossoms may be its natural cycle, since it is mid-August. Plus, it has been living in a pot. Next season, it will probably turn pink or purple before it turns brown.
This article will tell you how to deadhead your new plant. https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/deadheading-a-hydrangea.htm
I cut back a large hydrangea tree that came with our property. I don't know anything about it but it's very well established, looks like an actual tree, up to my garage roof, and used to have large white hydrangeas. It never showed any signs of life this year. Just a bunch of pruned branches now. Is this trash or is there any sort of hope?
The best thing that you can do is wait until next Spring. You will likely see signs of life from the roots!
If nothing happens by then, you can think about removing the tree and stump.
This article will help you with Tree Hydrangea care, in the even that your tree makes it through: