Project Property Helper Class

Constant Class

It is better to use one storage for all of hardcoded values like tid, vid, nid etc.
class ProjectProps {
  $DYNAMIC_PROPERTY
  const PROPERTY_NAME = 'static value';
  
  function setDynamicProperty() {
    $self::DYNAMIC_PROPERTY = dynamic_function();
  }
}

IN .module file put this on top - after that 
// Loading helper classes
module_load_include('php', 'project_core', 'class/ProjectProps');

$x = ProjectProps::PROPERTY_NAME;

Multiple references fileds query from one entity
$query = new EntityFieldQuery();
$query->entityCondition('entity_type', 'node')
  ->entityCondition('bundle', 'bundle_name')
  ->propertyCondition('status', NODE_PUBLISHED)
  ->fieldCondition('field_app_name', 'value', $value, '=')
  ->fieldCondition('field_app_ref_1', 'target_id', $value_ref, '=')
  ->fieldCondition('field_app_ref_2', 'target_id', $array(list of IDs), '=')
  ->fieldOrderBy('field_app_name', 'value', 'ASC')
$results = $query->execute();

// Example how to use EntityMetaData Wrapper
function get_node_field_values($node_object){
  $node_wrapper = entity_metadata_wrapper('node', $node_object);
  return array(
    'nid' => $node_wrapper->nid->value(),
    'title' => $node_wrapper->title->value(),
    'field_1' => $node_wrapper->field_app_name_1->value(),
  );
}

// Examples of how to use #states
$form['field_name']['#states'] = array(
  'visible' => array(
    '#field-selector_1' => array('value' => $value),
    '#field-selector_2' => array('!value' => '_none'),
  ),
  'required' => array(
    '#field-selector_1' => array('value' => $value),
    '#field-selector_2' => array('!value' => '_none'),
  ),
);