According to the CFPB, the three main credit bureaus used by most lenders do not include your prepaid card usage in your credit report. The prepaid card providers that claim to report your credit history usually only report to smaller used credit reporting agencies and not one of major three agencies.
The terms and conditions may be long and confusing, but it is important to read these before you get the card so you will know where your money goes.
When a prepaid card or gift card is unclaimed for a designated period, some states have escheatment laws that require the issuer to send the funds to the state of the last known address. The state can take custody of the card and add the value to the treasury's general fund until it is claimed by the rightful owner. The time of abandonment varies by state, but is typically two to five years.