Using Bellman$-$Ford, find the shortest path tree from the node $3$

the shortest$-$path tree consists of edges

the number of iterations of $BF$ is

renumber the nodes such that after renumbering $BF$ needs only $2$ iterations to find shortest path tree old number $1,2,3,4,5,6$ new number

the maximum number of iterations over all possible renumberings is $?$