Is there a species name on the label? That should help you research specific hardiness info.

A photo would be helpful, but it sounds like it might be Eucalyptus cinerea which comes from the Southern Highlands of NSW. Although it comes from a cool climate planted outside in your extreme cold could cause die back. However, this plant is adapted to wildfires and if damaged will reshoot from the trunk or, with severe damage, from the roots. The same happens if hit with extreme cold.

These Eucalyps grow very tall if not set back by climatic conditions. They can be pruned to keep them much lower and more spread out.

The important thing is to only give fertiliser which is specifically formulated to be low in phosphorus. Generally they don't have high fertiliser requirements.

Not even reliably winter hardy in my mild coastal zone. As described above, a hard winter will result in dieback to the roots, so typically this plant is almost always seen as a (sometimes) very large shrub. It just depends on the length of time until the next severe cold spell to determine how big this tree might get. In my area, I've seen them about 15'.