Does Umrah obligate Hajj, and if so, what should someone do who does not possess sufficient financial means for Hajj, while their limited means only permit them to perform Umrah, and the same applies to their mahram?

The 'Umrah is obligatory according to the soundest opinions of the scholars. Therefore, whoever is able to perform it, it becomes obligatory upon him to do so, even if he has not performed Hajj or is unable to combine them. A woman's ability to perform it includes the presence of a mahram. It is permissible to perform 'Umrah before Hajj or Hajj before 'Umrah.