Most of these questions are answered by the ruleset/lore of the source material (Werewolf: The Apocalypse) -
1) Almost all of the werewolves can fully morph between all 3 forms (Wolf - lupus, Werewolf - Crinos, Human - Homid). Later versions of the ruleset actually had forms in between those forms (so, like...halfway between giant werewolf and human, or halfway between giant werewolf and wolf form). All werewolves (garou) could freely shift between at any times except those born from the mating of two werewolves, which were locked to a single form.
2) The character in the game is a member of the Fianna tribe, which is s tribe of Irish/Celt werewolves. The Werewolf: The Apocalypse has a bunch of different "tribes" of werewolves, like Vampire's "clans", that, like a lot of RPG rulesets, act as stand-in for "races" and in a kind of similarly iffy way, determine the goals/temperament/etc. For instance, the Black Furies are a tribe of female garou who fight for women's rights, the Red Talons are a group of lupus-only separatist garou that don't believe in human societies, the Get of Fenris are a bunch of 'proud Germanic' warrior werewolves, and the Stargazers are a tribe of Hindu werewolves. Only the Uktena and Wendigo tribes are actually First Nations/Indigenous in the game.
3) This is honestly a kind of (or really) dicey thing about the Werewolf The Apocalypse ruleset: they fly really fast and loose with First Nations/Indiginous language. All of the werewolf groups are called "tribes", the meetings they have are called "moots", a lot of the basic tenants of the mythos of the werewolves in the game are based on sort of stereotypical First Nations stuff like "being connected to Gaia (the idea of nature)", how they fight against the encroaching industrialization of the land, a mysticism with "ancestors" and packs and family lineages and stuff. They play really fast and loose with it all and I have no idea what would classify as cultural appropriation, what would be cultural insensitivity, and what would be just taking the mythos of a group of people and "celebrating" it in a 90s style 'cool way'. I can't tell what's a celebration of it and what's a pastiche. They use terminology like "Cairn" to signify a meeting spot of werewolves, which is Gaelic, and there's a few other terms that are pulled from European tribal peoples as well....so it all sort of gets muddled with trying to make a connection between werewolves and early tribal peoples of a bunch of different ethnicities/lands. None of it seems like a mocking of these cultural aspects - the werewolves are pretty much always portrayed as righteous and "pure" (in a nature sense), which any sort of industrialization and technology is generally seen as "infecting" earth (though that has some real cultural knock-on problems as well).
But anyway - it's a potentially fraught ruleset/lore, and i'm curious whether this game will bring some more educated criticism of it.