Query of sales book number

Dear Expert

There is a query ,which is rarely asked,

• That is if it is mandotary required that in Start of Every Financial Year Sales Book Should be Started from 01 Number????? .........Or In a new financial year sales book number could be started as next number of  the last sales invoice number of last year (eg on 31mar12 invoice no 351 & on 1 apr 12 invoice no as 352 can also be raised )
• Legally and statutory  ..How many Type of Sales Book Can be mantained by business entity .??

Kindly revert..