negative inventory & tab or enter key

1. Yes: You can use the tab key to move past the fields for the current line, it will automatically add a new line and you can continue entering data. 
2. Yes/No: Yes, you can release an AP Bill against a PO without it being completely received.  No, it will not increase your quantity on hand and make it available to sell. 

Consider updating your availability calculation rules to make POs included in the available quantity before being received depending on your business requirements. 

My question was can you sell /release an AR Invoice have a negative quantity on hand for a while till the receiver enters the information 

On the AR side you would most likely need to enable Allow Negative Quantity on the item’s associated item class. 

Directly on an AR invoice only non-stock items are allowed so you will need to create a sales order and shipment, allow the inventory to go negative and create the AR Invoice. 

can you alos set required fields in let’s say the so entry form that afer you hit enter on the item number you are forced to enter the qty or uom if not you cannot go to the next  field let’s say the price ?

This can be done through a customization project. 

You can add a line to an SO or any detail screen by just hitting the down arrow too. no need to tab to the end of the screen. 

you can use tab to move to the right, shift tab to move to the left, F3 to open the finder, example to look for items. and up/down arrow to move from one line to the next, and down arrow will also add a new line.