Which of the following is$/$are true for heuristic functions in the context of adversarial search $?$

$1.$They can be learnt from data$/$experience for eg$.$ by playing games with another agent

$2.$They help deal with the problem of extremely large search depths in practice

$3.$They help reduce the worst$-$case time complexity of minimax search without comprising optimality against optimal

adversaries

$4.$They can be hand$-$engineered by humans$/$experts