get offline Bitcoin transaction id, chain multiple offline transactions let's say i create a valid transaction (offline without sending it, such as like this: http://brainwallet.org/#tx. let's call this "A"

a)before having sent A, can i get the transaction ID of A?

b)I wish to create a new offline Transaction (called B), using the outputs from A as inputs for B.Still, A has not been sent to the bitcoin network. Is this possible?  For example, A sends money from account x to account y.  B sends the same bitcoins sent from x to y, from y to z.

c) if part b) is possible, and I send A, then immediately send B to the bitcoin network. what would happen?
before having sent A, can i get the transaction ID of A?


Yes, you can calculate the TXID without any connection to the network. 


  I wish to create a new offline Transaction (called B), using the outputs from A as inputs for B.Still, A has not been sent to the bitcoin network. Is this possible?


Yes, but there's a small technicality when working with nested unconfirmed transactions. If you build a large number of them on top of each other, and one of them is never confirmed, then the entire chain of transactions will disappear. That is to say, if you build A, B, and C, and A had an incorrect fee, none of the subsequent transactions will ever confirm and will eventually drop from the network. 

That being said there's nothing stopping you from making chains of infinite lengths, they just have to be broadcast in order for the nodes to be able to see the previous inputs. If you make them out of order (C, A, B) they will likely be rejected. 


  is possible, and I send A, then immediately send B to the bitcoin network. what would happen?


This is completely valid and a reasonably normal flow for some applications, it's not invalid or unrecommended if the fees for each input are properly paid.