1. Tag tabs are taken from `sys_objects_tag` db table in the order they are in the table. First record in this table is default tab. You can set another default tab by doing small modification:
https://www.boonex.com/forums/topic/How-to-change-Tags-default-tab.htm
2. Spammy tag can be removed upon spammy content removing
3. By default there is no such functionality, but I think it should be small custom modification if you want this.
4. Photos are uploaded without adding any fields, only upon photo editing tags are set. You can set it mandatory on edit page by changing the following code in inc/classes/BxDolFilesModule.php file near ~432 line (but it will affect videos, files and sounds):
'tags' => array(
'type' => 'text',
'name' => 'medTags',
'caption' => _t('_Tags'),
'info' => _t('_Tags_desc'),
'required' => true,
'checker' => array (
'func' => 'length', 'params' => array(3, 128),
'error' => _t('_td_err_incorrect_length')),
'value' => $aInfo['medTags']
),