The verb "to reach" has several proper forms such as "reach for" and "reach out." Reach to is the same as simply reaching a limit. Reach at should not be used in place of reach for, but may be used colloquially as contact information (e.g. You can reach me at my home phone number.)
To reach a limit is to extend that far.
Example: "His property reaches to the river bank." (to is unnecessary)
To reach a point, a conclusion, a decision, or a destination is to get to or to arrive at one.
Examples: "He will reach town by noon." "The board could not reach a decision." "How can we reach the city?"
To reach someone is to make contact.
Example: "Have you been able to reach your sister?"
To reach out means to make an attempt.
Example: "The minister reached out to the community for help."
To reach for means to attempt, to stretch, or to extend.
Example: "He was reaching for the light switch." "Reach for the stars."
