[RPG] Can a paladin cast Speak with animals

No

As a wizard you gain the ability to cast wizard ritual spells as rituals, see ritual casting feature PHB page 114:

You can cast a wizard spell as a ritual if that spell has the ritual tag and you have the spell in your spellbook.

And the spellcasting subsection of multiclassing in the PHB says they are separate sets of spells for each class (page 164):

Spells Known and Prepared. You determine what spells you know and can prepare for each class individually, as if you were a single-classed member of that class.

The druid ritual casting feature is worded in a similar manner, so that they can only ritual cast druid spells.

There is no such thing in D&D 5e as "physical" damage. Damage reduces your hit points and comes in a variety of types but there is no mechanical difference between say bludgeoning and psychic damage - both cause loss of hit points.

"damage from spells" needs to be given a simple reading. Damage from a spell is the damage that is listed in the spell's description- that is the damage from the spell. Specifically, the damage from Bones of the Earth is damage from spells.

Examples of things that are not damage from spells is the damage done by summoned creatures, the damage done by a polymorphed creature or the damage done by teleporting someone 3 miles above the earth and letting them fall. This is because none of these sources of damage come from the spell description.