(1)
(NestList[#+1&,{0,2},2]//Flatten//Reverse)
(* {4, 2, 3, 1, 2, 0} *)
(2)
(NestList[#+1&,{0,2},3]//Flatten//Reverse)
(*{5, 3, 4, 2, 3, 1, 2, 0} *)
(3)
(NestList[#+1&,{0,2},#]//Flatten//Reverse)&/@Range[2,10]
(*
{
{4, 2, 3, 1, 2, 0},
{5, 3, 4, 2, 3, 1, 2, 0},
{6, 4, 5, 3, 4, 2, 3, 1, 2, 0},
{7, 5, 6, 4, 5, 3, 4, 2, 3, 1, 2, 0},
{8, 6, 7, 5, 6, 4, 5, 3, 4, 2, 3, 1, 2, 0},
{9, 7, 8, 6, 7, 5, 6, 4, 5, 3, 4, 2, 3, 1, 2, 0},
{10, 8, 9, 7, 8, 6, 7, 5, 6, 4, 5, 3, 4, 2, 3, 1, 2, 0},
{11, 9, 10, 8, 9, 7, 8, 6, 7, 5, 6, 4, 5, 3, 4, 2, 3, 1, 2, 0},
{12, 10, 11, 9, 10, 8, 9, 7, 8, 6, 7, 5, 6, 4, 5, 3, 4, 2, 3, 1, 2, 0}
}
*)