Is Jumu'ah prayer or Dhuhr prayer to be performed in a remote area where only 10 men gather for Jumu'ah prayer, knowing that the Hanbalis stipulate 40 men, while the Hanafis stipulate 3 men or more? And is it permissible for a Hanbali to adopt the Hanafi madhhab in this issue?

Jumu'ah prayer is not valid in a remote area according to the Hanafis unless it is a "misr" (a town with a judge). Their prayer is not sufficient, and they must repeat it as Dhuhr. As for the other madhhabs, it is not valid according to them with the aforementioned number (10 men); the Shafi'is and Hanbalis require forty, and the Malikis require twelve. Furthermore, permanent residency (istīṭān) is a condition for the validity of Jumu'ah according to the majority of jurists. Therefore, if the ten individuals are not permanent residents, Jumu'ah is neither obligatory for them nor valid from them, and they must repeat it as Dhuhr.