Do I get to select the spells known by my Faerie Dragon Familiar?

[LessPopMoreFizz]

The Faerie Dragon 'casts spells as a 3rd level Sorcerer'.

When taking one as a familiar, do I get to select and change it's spells known from those indicated in the stat block? For instance. Could I, for instance, give it Detect Magic instead of Flare, or Mending instead of Open/Close, or Enlarge Person instead of Grease?

Additionally, can the Faerie Dragon use magic items as a sorcerer without relying on UMD? What about items like a Page of Spell Knowledge to expand its spell list?

(To be clear, I AM NOT asking about whether this spell casting ability scales. That's a seperate question, and one which I'm less worried about.)

[Nefreet]

It gets the default statblock spells, unless your GM rules otherwise.

This means it can use wands and such just as easily as a Sorcerer.

You can even feed it a Page of Spell Knowledge.

[Lao Haeris]

by RAW you are not allowed to change its spells.
Most DMs (non-PFS) will allow you to customize it's spell list though, if you give them cookies. Cookies always work with DMs.