Its spelt 'linear'. And even with the first few fallouts, you can decide what life your character had. With Fallout 3, you have your entire life played out for you, so its annoying for some to have the same background for every character they play. For the Vault Dweller and Chosen One, the presets each have a different backstory, and have their own reasons for leaving the vault/village. In fallout 3, you have the same father, same friends and can't choose how you grew up in the vault.
Nazi? If you want to be like that, its is actually spelled "it's"
Back on topic
In my opinion they shouldn't give you a certain age, because, well who is a 19/20 year old with a huge beard, and on top of that looking as old as a grandfather? Though it does fit in with the story, you can make your person look older then your father.