Haftsa Daisoura

Have a good week!
Why is there no law to prevent a minor from committing prohibitions (but only from making a forbidden mistake), and after all, the Rabbis taught us that in addition to the warning of the prohibition, there is also a real desire (and it does not matter whether we define it as a poison or as a Maral that the Torah commands us to do so), and therefore we prevent him from harming the desire?
Can we learn from this that the law of Aphrodisias from Isura is about the warning or rebellion and not about the harm to the object itself?
And especially according to the Reka, one should be excluded from engaging in sexual intercourse even though it does not violate a prohibition, because it actually violates the hafza (apart from the prohibition of Shabbat, which is all about a deliberate act)?
Although it is possible to argue from the words of the Shach and Sha'a that it is better to prevent infants from breastfeeding non-Jews since it is 'a mouth that will speak with the Shekhinah', why is there really no law to exclude?
thanks