Irrecoverable and Doubtful debts

Can you please say whether these are correct statements.

(1) When someone becomes irrecoverable we remove the receivable of that customer at the time we realize they are not going to pay by making this entry.

DR Irrecoverable expense
CR Receiveable

(2) When someone becomes doubtful we make allowance against the receivable of that customer at the year-end by making this entry.

DR Irrecoverable expense
CR Allowance For Receivable

(3) When the cash is received from the irrecoverable customer then we should remove the irrecoverable expense that we made last year in Year 1 by making this entry only.

DR Cash
CR Irrecoverable expense

(4) When the cash is received from the doubtful customer then we should record cash and remove allowance that we made last year in Year 1 by making this entry.

DR Cash
CR Receivable

DR Allowance For Receivable
CR Irrecoverable expense