use budget except for specific commitment item

I have two questions for you

Firstly,

I don't want to use budget in specific commitment item

How can I except for it?

this commitment item's financial trans is 50, and commitment item cat is 2

and I can see it from FMIFIIT table but I don't

I usually use this asset retirement, tranfer or acquisition

before I upgrade SAP version from 4.7 to ECC 6.0, It didn't happen

Secondly,

After PO, I canceled it but still grab some budget

and I can't use that budget anymore

How can I back to my budget before PO?

Thanks in advance