What spells can not be found as loot in Skyrim

The system is levelled - you won't find hugely difficult things you cannot beat. Except giants.

Actions that level up skills:

• Attacking someone with a weapon
• Casting a spell on someone or something (things like Clairvoyance do nothing)
• Sneaking and not being seen in the presence of enemies
• Opening a lock - seems breaking a lockpick also gives skill xp
• Picking a pocket
• Buying or selling something.
• Successfully persuading/intimidating someone
• Training
• Some quest rewards (Finding Amren's family sword gives you +1h and +block)
• Creating a piece of armour or a weapon, or improving one
• Enchanting/disenchanting something
• Taking damage whilst wearing armour
• Making a potion or a poison

The list isn't exhaustive, though.

I can unequip both spells by clicking right once, to remove the off hand, then left to remove the main hand. Did no have problem with this.

Do understand that :

• You need to highlight the currently selected spell in the hand you want to remove
• Click with the mouse button corresponding to the hand you want to remove the spell from

Adding sequences:

• Spell () + Mouse L = Spell (L)

• Spell () + Mouse R = Spell (R)

• Spell (R) + Mouse L = Spell (R, L)

• Spell (L) + Mouse R = Spell (R, L)

Removing sequences:

• Spell (R, L) + Mouse L = Spell (R)

• Spell (R, L) + Mouse R = Spell (L)

• Spell (R) + Mouse R = Spell ()

• Spell (L) + Mouse L = Spell ()