2010-11: Julio Billia played bantam hockey in Montreal and was one of 42 players selected to attend the inaugural Allstate All-Canadiens Mentorship Camp in Mississauga, Ontario.
2011-12: Billia played for Laval-Montreal in Quebec midget AAA hockey — sharing the goaltending duties with William Corbeil. Billia was 7-12 in 23 games and had a 2.85 goals against and .908 save percentage. Laval-Montreal finished last in the CCM Division. Billia was selected by Chicoutimi in the second round (29th overall) of the 2012 QMJHL Entry Draft.
2012-13: Billia spent most of the season in the QMJHL with Chicoutimi — appearing in eight midget major games with Laval-Montreal — and played for Canada Quebec in the 2013 U17 World Hockey Challenge. He was 9-6 with 1 shutout in 22 games as a backup to Christopher Gibson (TOR) with the Sagueneens; posting a 3.18 goals against and .888 save percentage. Billia didn't face any shots in nine minutes of action in his only playoff appearance in Chicoutimi's first round series with Quebec. He was 5-2 with a 2.87 goals against and .907 save percentage in midget play with Laval-Montreal. Billia had a 3.50 goals against and .905 save percentage in four games at the WHC for Canada Quebec.
2013-14: Billia played for Canada's gold medal-winning U18 team at the 2013 Ivan Hlinka Memorial Tournament in August before returning to Chicoutimi for his second season with the Sagueneens. Billia finished the Ivan Hlinka Memorial Tournament with a 1.58 goals-against average and .919 save percentage, capping the tournament with a 21-save shutout in Canada's 4-0 win over the USA in the gold medal game.