Do I need to show the proof of travel for the Schengen Visa?

Hello everyone,

I wonder if I(family member of EU citizen) must show the proof of travel(tickets) and accomodation for the application of the Schengen visa for any country?

which country is not so problematic?

I want to travel to Slovenia next year in March for a weekend to visit a friend but also would like to go to a concert in Italia in April, my EU partner cant go with me due to work at that time.

I am not sure but I have been reading some embassies and they state that I have to show everything( travel documents , accomodations, addresses, etc... if I travel alone?

Please help.

Thank you