Write a SOQL query that counts the number of active Contacts for each Account in a set.

Hi Every One,
Kindly provide  expected solution to below queries.

Declaratively create logic in your org that prevents two Opportunities from being created on a single Account in a single day.
Declaratively create logic in your org that prevents closed Opportunities from being updated by a non System Administrator profile.

Many Thansk in advance.

Write a SOQL query that counts the number of active Contacts for each Account in a set.

Hi Every One,
Kindly provide  expected solution to below queries.

Declaratively create logic in your org that prevents two Opportunities from being created on a single Account in a single day.
Declaratively create logic in your org that prevents closed Opportunities from being updated by a non System Administrator profile.

Many Thansk in advance.