Is access sequence mandatory for Manual text types

Hello,

we need to define a new text id in sales order header. Users will be manually inputting the same in sales order. Two questions

1)) Do one needs to define an access sequence for the new text id if user needs to manually update the text in sales order ?

2) If a header delivery block in sales order exists, then only users need to mandatorly enter the text manually but if there is no delivery block, then user are not suppose to enter the text. I can make the text as obligaory but that will be for all sales orders whether delivery block exists or not. So can the text requirment routine helps in this case ?

regards

Sonu