Toyota Estima Why have all the dashboard warning lights and alarm sounding?

We picked this up last week drove 20 miles home, it had been sat around in the snow so replaced the battery as needed it to be reliable (a 1993 k reg). Did one school run after and it was fine, next day got diesel and after about a minute alarm sounding inside car and all dashboard lights lit up. I definitely put in diesel.

Could it be something to do with immobiliiser after changing alarm?

We have no manual either. Please help!!