Question: What generation of a hybrid cat which is a cross between a serval and domestic cat is the first to be considered a domestic cat legally?

Context paragraphs:
Highlander cat: The Highlander (also known as the Highlander Shorthair, and originally as the Highland Lynx), is an experimental breed of cat.  The unique appearance of the Highlander comes from the deliberate cross between the Desert Lynx and the Jungle Curl breeds, also recently developed.  The latter of these has some non-domestic ancestry from two Asian small cat species, the leopard cat and jungle cat, making the Highlander nominally a feline hybrid, though its foundation stock is mostly domestic cat.

Exotic felines as pets: Hybrids of the domestic cat with non-domestic species (e. g. the Bengal cat or the Savannah cat) are not normally considered wild cats.  While this distinction is often overlooked in the media and in the public eye, such cat breeds (especially the F5 and subsequent generations) are much closer to the domestic cat in terms of housing and husbandry requirements, behavior, and legality.

Tabby cat: A tabby is any domestic cat that has a coat featuring distinctive stripes, dots, lines or swirling patterns, usually together with a mark resembling an 'M' on its forehead.  Tabbies are sometimes erroneously assumed to be a cat breed.  In fact, the tabby pattern is found in many breeds, as well as among the general mixed-breed population.  The tabby pattern is a naturally occurring feature that may be related to the coloration of the domestic cat's direct ancestor, the African wildcat, which (along with the European wildcat and Asiatic wildcat) has a similar coloration.

List of cat breeds: The following list of cat breeds includes only domestic cat breeds and domestic × wild hybrids.  The list includes established breeds recognized by various cat registries, new and experimental breeds, distinct domestic populations not being actively developed, and lapsed breeds.  s of 2016, The International Cat Association (TICA) recognizes 58, the Cat Fanciers' Association (CFA) recognizes 44, and Fédération Internationale Féline (FIFe) recognizes 43.

Bengal cat: The Bengal is a domestic cat breed developed to look like exotic jungle cats such as leopards, ocelots, margays and clouded leopards. Bengal cats were developed by selective breeding from hybrids of the Asian leopard cat (ALC), "Prionailurus bengalensis bengalensis", with domestic cat, backcrossed to domestic cats, with the goal of creating a confident, healthy, and friendly cat with a highly contrasted and vividly marked coat.

Savannah cat: The Savannah is a hybrid cat breed.  It is a cross between a serval and a domestic cat.

Serval: The serval ("Leptailurus serval"), also known as the tierboskat, is a wild cat found in Africa.  It is the sole member of the genus "Leptailurus" and was first described by German naturalist Johann Christian Daniel von Schreber in 1776.  Eighteen subspecies are recognised.  The serval is a slender, medium-sized cat that stands at the shoulder and weighs .  It is characterised by a small head, large ears, a golden-yellow to buff coat spotted and striped with black, and a short, black-tipped tail.  The serval has the longest legs of any cat relative to its body size.

Aegean cat: The Aegean cat (Greek: γάτα του Αιγαίου "gáta tou Aigaíou") is a naturally occurring landrace of domestic cat originating from the Cycladic Islands of Greece.  It is considered a natural cat, developing without human interference.  Development of the Aegean cat as a formal breed began in the early 1990s by breeders in the fledgling Greek cat fancy, but the variety has yet to be recognized by any major fancier and breeder organization.  It is considered to be the only native Greek variety of cat.

Sokoke: The Sokoke (or Sokoke Forest Cat in long form, and formerly the African Shorthair) is natural breed of domestic cat, developed and standardised, beginning in the late 1970s, from the feral khadzonzo landrace of eastern, coastal Kenya.  The Sokoke is recognized by four major cat pedigree registry organizations as a standardised cat breed.  It is named after the Arabuko Sokoke National Forest, the environment from which the foundation stock was obtained, for breed development primarily in Denmark and the United States.  The cat is long-legged, with short, coarse hair, and typically a tabby coat, though specific lineages have produced different appearances.  Although one rumored to be a domestic × wildcat hybrid, genetic study has not borne out this belief.  Another idea, that the variety is unusually ancient, remains unproven either way.  The native population is closely related to an island-dwelling group, the Lamu cat, further north.

Serengeti cat: The Serengeti is a breed of domestic cat, first developed by crossing a Bengal (domestic and wild hybrid) and an Oriental Shorthair.  Recognized and registered by The International Cat Association (TICA), no other first generation crosses can be registered as Serengeti.  From the Bengal × Oriental cross came the first foundation Serengeti.  Breeders then worked with the cat to produce a cat that resembles the breed profile set by TICA.

Supporting paragraphs: Exotic felines as pets Savannah cat
Answer: F5