[Sticky] What Can Familiars Do in the Griffons Den Shared Campaign?

The question of what familiars can-or-can-not do is a difficult one. Can an owl familiar wield a wand or administer a potion? What about a snake? Or a cat? Or a spider?

The RAW is mostly silent on this topic, and His Holiness JC (Jeremy Crawford of course, not that other JC guy) has not weighed in to clarify these questions.

WHAT WE KNOW:

We can say categorically that familiars can attune to objects and have 3 attunement slots like all other creatures. We also know that, while normal (non-Pact of the Chain) familiars can not "attack," (the universal RAW definition of an "attack" is a D20 test against AC, thus a saving throw is not an "attack") they can do other actions that are not vs. AC, such as use a wand of magic missiles or a helm of brilliance.

The RAW leaves it up to the DM to decide if a particular familiar has the necessary body structure to perform certain tasks. For example, in the past I have ruled that some sort of opposable or gripping digit was required to administer a potion, so the Pact of Chain familiars generally have thumbs or thumb analogs, and could therefore administer potions, but basic familiars such as an owl, hawk, snake or spider could not. So long as the rule was applied consistently that was fine, however now that we have multiple DMs running multiple tables we are starting to see wide table variations. This creates expectations and uncertainty at the table, so it is necessary to create a standardized set of rulings on these questions that will harmonize across all games in the Griffons Den Shared Campaign, allowing both players and DMs to have shared expectations on these grey areas.

SHARED CAMPAIGN STANDARDIZED RULINGS

1. All familiars may attune to 3 magic items like any other creature. These slots are their own, not part of the owner's slots (that was an old AL homebrew rule and is not RAW).
2. All familiars are magical spirits and can wear or wield magic items, including wands, potions and other items, unless the familiar literally lacks the necessary body parts (ie. a snake wearing boots or gauntlets). Even then, clever narrative could get around this mechanical problem (a snake can wear a ring around the tail, or an octopus around it's tentacle). Regardless, it falls to the player to narratively describe how this is happening, and all DMs should reward creativity and fun storytelling, applying this rule as permissively as possible. 
3. All magical items and/or gear will resize magically to fit familiars, just as with any other creature.
4. All familiars can administer potions to others, but again it is up to the player to narrate exactly how this happens.
5. Familiars or other creatures may hide inside an enclosed space, such as a backpack, bag of holding, or clothing. This provides full cover and functionally protects the creature from external effects or damage such as breath weapons or AoE effects.
6. Find Familiar is a level 1 spell. The Spellwrought Tattoo (1st Level) is a single use, non-attunement Common magic item that anyone can buy and use. Common magic items cost 100 gp. YOU'RE WELCOME! ;p