Toph, Earthbending Master

If the targeted land becomes an illegal target before the spell or ability that includes earthbend resolves, earthbend does nothing. If the spell or ability didn't have other targets, it won't resolve.

Earthbend doesn't give the land you control a color. As most lands are colorless, in most cases the resulting land creature will also be colorless.

All experience counters are identical, no matter how you got them. For example, the last ability will count experience counters that you got from the first ability, from another ability, from another copy of Toph, Earthbending Master, and so on.

The land will retain any other types, subtypes, or supertypes it previously had. It will also retain any mana abilities it had as a result of those subtypes. For example, a Forest that's turned into a creature this way can still be tapped for {G}.

The experience counter goes on you, the player, not on Toph. You will keep that counter even if Toph, Earthbending Master dies.

"Earthbend N" means "Target land you control becomes a 0/0 land creature with haste in addition to its other types. Put N +1/+1 counters on it. When it dies or is exiled, return it to the battlefield tapped under your control."

You may target a land that is already a creature, perhaps because of a previous earthbend ability. The land will get the +1/+1 counters, gain haste, and have its base power and toughness set to 0/0.

If a land was animated by earthbend and would go to any zone other than the graveyard or exile, it will not be returned to the battlefield by the delayed triggered ability created by earthbend.