It's a Jewish organization that supports Modern Orthodox Jewish life.
Union of Messianic Jewish Congregations was created in 1979.
The U inside a circle (actually the letter O) stands for The Union of Orthodox Jewish Congregations (OU). Indicating the product has been certified by them as being kosher.
They aren't forbidden to do so, it is just the custom that developed.
Union of Nazarene Yisraelite Congregations was created in 2000.
Abandonment of orthodoxy does not make a Jew non-Jewish. It just means that they find the Orthodox interpretation of Halacha, Jewish law, to be too confining. Many former Orthodox Jews end up joining non-Orthodox congregations, while others may abandon all Jewish observance and become secular Jews, still identifying strongly as Jews while largely ignoring Judaism as a religion.
Hebrew is the ancient language of the Jewish people. Second, not all Orthodox services are only in Hebrew. Most congregations have at least some English, usually the sermon and the Prayer for the country. Furthermore, Reform and Conservative services today also contain a large amount of Hebrew.
Orthodox Union was created in 1898.
No, it is part of The Orthodox Church (Christianity), and it is not Jewish. In fact, there is no such thing as a Jewish church.
My Orthodox Jewish grandmother married a Reform Jewish man.
Association of Orthodox Jewish Scientists was created in 1947.
Union of Orthodox Rabbis was created in 1901.
I'm not sure what you mean by "followers" but there are 3 primary branches: Orthodox, Reform and Conservative. There are communities and congregations within each of these branches that vary also in how strictly they interpret Jewish laws and writings.