Is it illegal to take out an installment loan to pay for bankruptcy and attorney fees and not include it in the bankruptcy?

In a bankruptcy, you file on all your debts. You don't have the right to pick and choose which debts are included. Some debts, like mortgages and car loans, you can keep so you keep the property but unsecured installment loans can't be reaffirmed. If you take out a loan that you don't intend to repay, the bankruptcy court can deny your discharge.

Yes.

On your bankruptcy papers you must include every single debt or claim you have and disclose all your property. If you take out a loan shortly before filing a bankruptcy in order to pay for it, then you must pay that debt. Otherwise you will have committed fraud. And that can get you into a lot more trouble.