Idaho is among states eyeing a $500 million federal grant competition to improve preschool education programs.  But how exactly the money could be spent in Idaho, which does not fund a statewide pre-K program, remains uncertain as officials wait for the U.S. Department of Education to release criteria for the competition. Idaho officials have also been leery in the past about any strings attached to accepting federal grant money. Education Secretary Arne Duncan announced the Early Learning Challenge in May and the Idaho responded last month, saying the state intended to apply.     At least three other states that don't fund pre-K programs - Hawaii, Wyoming and Mississippi - also plan to compete.      Education experts say those states could still use the grant money to improve their systems of early learning.