The answers I can give you, for now:
On your 1.0.0 3DS: You can't update it to 4.X - 9.2 without using a game card to update. You will have to buy something.
On your 10.3 3DS: There's nothing you can do right now, if you don't have the first version of Ironfall Invasion, Cubic Ninja, or Ocarina of Time 3D(plus Powersaves if you don't already have oothax installed).
On your 7.2 3DS: You can follow the guides linked and get CFW. Just for the love of god don't update that.
If you'll use the 7.2 3DS for CFW, etc., I ask you not to update your 1.0.0 3DS so its NAND can be dumped in the future. If you don't feel confident or don't have the resources to do a hardmod, is selling it to someone who will an option?