Casting from under the ground or inside a stone wall ?

[Phasics]

So Stone Oracle

Earth Glide to get in and out of earth and stone at will

Crystal sight to see creatures while your inside said earth or stone.

Wall of Stone to create a wall of rock you can earth glide into when stuck inside surrounded by worked stone.

When your on earth n dirt just drop into the ground and hang out just below the surface.

Now I feel like the grey area is going to be line of effect. How close to you need to be to the surface of the rock/earth not to be blocked by said stone or earth. Reach outside at the completion of the spell and pull it back in as a free action ?

You can breath inside the stone so in theory you can speak and the vibration would travel into the stone so the verbal component should be satisfied even if no one else hears you.

Also the blackened curse for scorching ray and clobbering strike seems like a fun way to get three 1/20 tries at a trip attempt per casting.

[Pizza Lord]

Assuming you can see from inside the ground/stone, then yes, line of effect is likely the only thing stopping you from making attacks or casting spells on targets. You would likely need to at least lean out of the stone or extend a hand or emanating body-part to make the attack or cast the spell (I would imagine similar to an incorporeal creature striking from inside an object.) A foe could ready an action to attack you as you do so. They wouldn't be able to disrupt the actual casting if you can do that while in the object, but when you extend the hand or lean out or rise up they could strike (but that won't end the spell, since it didn't interrupt it.)

[wraithstrike]

You are either in a square or you are not. A GM can say you lean to bypass line of affect, but by the rules the square you are in, the square the target is in, and whatever is between you is what will determine if you have line of affect.

If the barrier give the target total cover then the spell can not pass through it.

[Diego Rossi]

Look the rules for water and being submerged. The situation is very similar.
You can't stay submerged, stick out an and and cast while retaining total protection, but you can get this set of benefits:
"Attacks from Land: Characters swimming, floating, or treading water on the surface, or wading in water at least chest deep, have improved cover (+8 bonus to AC, +4 bonus on Reflex saves) from opponents on land. ..... A completely submerged creature has total cover against opponents on land unless those opponents have freedom of movement effects. Magical effects are unaffected except for those that require attack rolls (which are treated like any other effects) ....."

(I have cut off the parts about freedom of movement and fire)

LOF/LOS are reciprocal (barring special effects like Crystal sight, but that work only for LOS), if you have LOF, your target has it, too.

[Phasics]

Would it be weird taking flyby attack with a fly speed from some source and diving in and out of the ground loosing a spell in between .

[Pizza Lord]

Universal Monster Rules wrote:

Incorporeal ...An incorporeal creature can enter or pass through solid objects, but must remain adjacent to the object’s exterior, and so cannot pass entirely through an object whose space is larger than its own. It can sense the presence of creatures or objects within a square adjacent to its current location, but enemies have total concealment (50% miss chance) from an incorporeal creature that is inside an object. In order to see beyond the object it is in and attack normally, the incorporeal creature must emerge. An incorporeal creature inside an object has total cover, but when it attacks a creature outside the object it only has cover, so a creature outside with a readied action could strike at it as it attacks. An incorporeal creature cannot pass through a force effect. ...

While obviously Earth Gliding and Incorporeality are not the same thing, I am pretty sure the rules for one are the closest you are going to find to a reasonably similar situation.

[Snowlilly]

Use the incorporeal rules. Same action, different mechanic.