What are the legal and شرعي (Islamic legal) implications of divorcing a girl by phone, who is my fiancée and before consummating the marriage, knowing that the Mufti issued a fatwa that it is a minor irrevocable divorce (طلاق بائن صغرى), and the divorce has not been registered in court?

If the marriage contract (nikah) was concluded with all its pillars, then your divorce is effective even if it was not documented. According to Islamic law, the following consequences result from this divorce:

1. The wife is entitled to half of her dowry, based on the Almighty's saying: "And if you divorce them before you have touched them and you have already specified for them an obligation [of dowry] - then for them is half of what you specified, unless they forgo it or he in whose hand is the marriage contract forgives. And to forgo it is nearer to righteousness. And do not forget graciousness between you. Indeed, Allah, of what you do, is Seeing." (Al-Baqarah: 237).

2. A minor separation (baynunah sughra). Divorce before consummation means that the wife is not permissible for you except with a new contract.

3. Muta'ah (a compensatory gift) according to some scholars, which is a sum paid to the wife to console her, and it is determined by the husband's financial ability.

As for the legal aspect, specialists should be consulted, knowing that divorce can be permissible, disliked (makruh), or forbidden (haram).

It should be noted that divorce does not occur if the anger was so intense that one lost awareness of what was being said.