Hi experts
in joomla 3 i know jquery declaration is added by default by the joomla.One have to place one simple call in their extensions by JHtml::_('jquery.framework', false); to include jquery.

My question is whether this call made by different third party extensions or template, is jquery declaration included only once for sure? what is the correct way of declaring jquery in joomla 3 custom extension to avoid conflicts as we know there are two of declaring jquery like JHtml::_('jquery.framework'); and JHtml::_('jquery.framework', false); ? different extensions may include one of these declarations also is joomla 3 loads jquery by default without any call from extensions or templates?

Thanks in advance