No he cannot alternate anywhere
Full time EHF players can not be alternates on any other team in any other league. The only exception is that they can play for their town/school team. Rules are on the EHF web site.
EHF Elite kids are not allowed to play anywhere but their EHF Elite team or their town team. Any crossover to another "Elite or AAA" program is done at own risk. It is done at all age levels, just remove the stickers from your kid's helmet and get a plain hockey bag (no team insignia), use the back and side doors to the rinks, stay out of the stands, keep your mouth shut, and get your kid a tinted or white visor so his face is hard to see. Then deny, deny, deny. It's a lot of aggravation, just skate your kid in as many skills as you can if you want to get him more ice.
5, 7, and 10 are all good that’s three levels
He can play for his town or school.
EHF elite please.. it's like an alternate dimension. Much like Keano Reeves in the matrix.