i recommend too aim for iruka or sasuke even if you can only get like 10 fragments for one. The reason is they repeat such events often or new events with iruka and sasuke. This way you can get them if you get now some and later some .... and so on.

No you cant you have 7 free tries you probaly wont even get 5 fragments.

GL with that strategy almost all events are like this everytime RNG. Thats what makes you addict too it.