Players signed before age 18 are signed to youth contracts which are not valid for more than three years, according to FIFA regulations. So we can't have signed him to a six year deal, unless he has options after year three making it non-binding. (regulation 18.2)
Even if he were of age, the maximum binding length of a FIFA-sanctioned deal is five years.... so we can't have signed him to six.
International Transfers are only permitted over age 18, except where parents are accompanying the teen to live and an exception has been granted by FIFA.
https://www.icsspe.org/system/files/...%20Players.pdf