Is it permissible to act upon the fatwas found in an old edition of Shaykh Al-Tareefe's book "The Prophet's Prayer Described," or to act upon an old fatwa published on the website, if a newer edition or fatwa exists that may include revisions?

There is no blame upon you for acting upon the fatwa you possess, and you are not obliged to search for another edition to ascertain whether the mufti has changed his fatwa or not.

It is generally the case that later fatwas are more precise; therefore, it is preferable to search for new fatwas first. If none are found, then you may act upon previous fatwas.

Some scholars have elaborated on the necessity of re-inquiring for one who was given a fatwa concerning an incident that later recurred. Some of them believe in the necessity of re-inquiring in specific cases due to the possibility of a change in the mufti's opinion, while others believe there is no need for re-inquiry as long as the ruling is known and the original stance of the mufti is presumed to remain.