I've checked your decanter against the Greek Key examples in the Molineaux Webb pattern book, which has several Greek Key designs, but it's not a match.
I'm not an expert on decanters but I'd guess circa 1870 for this one. Both the Greek Key and the leaf & grape design on your request #2 are widespread patterns and virtually impossible to pin down to any manufacturer. Also the one in #3 looks fairly standard, which I guess is why nobody has had a guess at them. I've not read it but I believe Andy McConnell's book on decanters is the definitive guide if you can find a copy...