Advice on Creditor Insolvency Please

I am giving employment training for advisers and need to say something about
making the employer insolvent in order to claim from the National Insurance Fund.

Insolvency is not my field and I would be grateful for help with the following questions:-

1.I assume the fee for winding up a company or bankruptcy ranks first
in the insolvency and is potentially recoverable if there are sufficient assets

2.What is the deposit for? (I’ve never understood this)
Is it also potentially recoverable?

3.The £5000 limit for bankruptcy and the £750 limit for winding up
a company are expressed as a debt or “a share of debts”.
Do there have to be statutory demands or judgments for sums
totalling over these limits? Or can a debtor just say “I know there are
other debts which together add up to more than £5000 / £750”?

Many thanks

Haven’t given debt advice in a while, so of limited use here.

The deposit is to cover admin costs. If there are sufficiend assets for creditors, it is the first thing that will be returned to the petitioner.