The number of transpositions between two permutations

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Suppose it is possible, through many steps, to move from the permutation $\pi$ to the permutation $\sigma$ by multiplying, at each step, by a transposition.

Knowing that they are not necessarily conjugates, I want to find:

  1. In how many ways (The maximum number) I can move from $\pi$ to $\sigma$.

  2. bound the maximum number of steps needed to switch from $\pi$ to $\sigma$ (is there a reference).

EDIT 2 In other words, as Peter Taylor proposed:

Let $d(\pi,\sigma)$ be the length of the smallest sequence of transpositions we need to multiply by the permutation $\pi$ to take it to $\sigma$.

  1. How can I bound or even calculate the number of sequences of length $d(\pi,\sigma)$ which take $\pi$ to $\sigma$? (I am looking for any idea)

  2. How can I bound or even calculate $d(\pi,\sigma)$ (This one is answered as explained above)?

It is known that the number of transpositions in the symmetric group $S_n$ is $\frac{n(n-1)}{2}$ and also it is possible to decompose a certain permutation into disjoint cycles, but I don't how to collect these results to answer my question!

Any kind of help is appreciated.

EDIT 1: I don't think my question is a duplicate! it consists of two parts and the marked question answers only one question! The linked question is not talking about the first part of my question!