There is a soapberry/buffalo berry that grows in cold climates. What kind can I grow in zone 2?
Yes, soapberry will do well in your area. Here is an article for more information on some plants that will do well in your area: https://www.gardeningknowhow.com/garden-how-to/gardening-by-zone/zone-3/plants-for-zones-2-3.htm
Can we use soapnut liquid instead of horticulture soap or can we use it in place of liquid dish soap in preparation of neem oil foliar spray ( ie; neem oil + liquid dish soap + water ) ?
Absolutely! This is common practice. Here is an article that will offer more information on the tree:
I bought a Western soap berry tree in 2009 and it is the 2nd yr. of producing berries. I even boil them to make suds but I don't get any.
Soapberry has translucent fruits in fall and winter that contain saponin, which causes the fruits to soap up when crushed or sliced in water. Is it possible you have a Chinaberry tree instead of soapberry? They are very similar and often confused. Chinaberry trees have lavender flowers in spring and Soapberry has cream colored flowers. Chinaberry fruit is opaque during the winter.