I'm not to sure about the F1 but i think its to do with the strain being stable meaning that the strain has been bred a few times until the wanted traits show dominant in the finished plant
And clone only does what it says on the tin , It is only available in clone no seeds of the plant strain exist most clones would be taken off a mother plant which must have been the shit ,if the plant is crossed with another , it is no longer the original mother strain but a cross ,which is why some strains are clone only
Hope this helps
F1 hybrid is a term used in genetics and selective breeding. F1 stands for Filial 1, the first filial generation seeds/plants or animal offspring resulting from a cross mating of distinctly different parental types.[1] The term is sometimes written with a subscript, as F1 hybrid.[2][3] The offspring of distinctly different parental types produce a new, uniform variety with specific characteristics from either or both parents. In fish breeding, those parents frequently are two closely related fish species, while in plant and animal genetics those parents usually are two inbred lines. Mules are F1 hybrids between horse and donkey.
also Definition: The F1 (first filial) generation is the hybrid offspring produced in the cross pollination of P generation plants. fromhttp://biology.about.com/bldeff1gen.htm that may be a bit more reliable of a source than wiki