Thanks for the questions on Maggie!
1) Yes and 2) No. -> This follows the same logic as General Store, which if a card effect attaches a goods/spell you may attach the attachment to a booted dude or even in a place you don't control.
3) You still do need to pay the costs of inventing.
4) I'm not sure I follow completely here, but will try to answer. Any card effect--traits or abilities--that attach a goods/spell, allows you to attach said goods/spell to a booted dude, and regardless if you control the location where that dude is at or not. This does not override any additional costs and constraints about those goods/spell. Like with gadgets, you still need to pay the costs of inventing ( i. boot a MS, ii. pay GR cost of the gadget, iii. perform a skill test using the MS's skill rating).
Totems) Totems that are attached by a card effect (Owl's Insight for example), still need to satisfy the additional costs/requirements of Totem planting (i. must be attached to a location you control, ii. must have an unbooted shaman at that location.). So while a General Store would allow you to attach at location you don't control (which loosens the restriction on where you can attach), the Totem planting still requires you to attach to a location you control (which tightens the restriction on where you would attach. The net result: You must still attach the totem to a location you control (and have an unbooted shaman there).
Hopefully this clarifies some, if there's any follow up questions, please let us know!