Definition of "Full-Scale Regional War": A "full-scale regional war" in the context of this question is defined as active, sustained military conflict involving at least three sovereign nations within the Middle East region, with these countries officially declaring war or being widely recognized as being in a state of war.
Duration of Conflict: The conflict must last for at least 30 consecutive days, with ongoing military operations and significant engagements between the involved countries.
Geographical Scope: The conflict must encompass significant military actions in multiple locations across the Middle East, not just isolated skirmishes or border clashes.
Mainstream Media: The occurrence of such a war must be verified by at least three credible international news organizations, who explicitly or implicitly call it a wider war. (e.g., BBC, Reuters, Al Jazeera, CNN).
For the purpose of this question, is Palestine a sovereign nation?
Is Yemen at war?
Palestine is a non sovereign nation and the ongoing conflict in the area of Israel and Palestine is a local conflict not a regional conflict
The important part of the question is "regional war in the Middle East" as in its all encompassing of the countries in the middle east
Id like to address the yemen part of your question. To be clear yemen has declared war on israel, but israel hasn't reciprocated. Israel as yet is only conducting retaliatory strikes in Yemen as opposed to the situation in gaza. So, for the purpose of this question all parties involved have to declare war on each other and conduct sustained military campaign inside each others territories thst aren't retaliatory strikes