The competitions are in age groups which you will fit into.
There is no minimum age
There is no need for any handicap or club membership to play in the flag events. The age groups in flag events are Boys Under 8, under 10, Under 12, Under 14 and for Girls Under 10 , Under 14 and Under 18
For the 9/18 hole short course stroke play events which are generally on the same time as the flag event each child must complete a flag course in 36 shots, at least twice on different courses to qualify for this. The age groups in this are for boys Under 10, Under 12 and Under 14 for girls it is Under 14 and Under 18.
The under 15 and under 18 opens for boys and Under 18 Open events for girls, would require you to be a member of a club and have an official CONGU handicap.