Best Trade Solution

I have three questions.Please explain these briefly:

01. When does a nominated bank can honor?
02. Why nominated Bank is the agent of issuing bank?
03. "Issuing bank cannot play the role of nominated bank.Except article:38" why??

Briefly
01. because it purchases docs not honors
02. because it has been so authorized by issuing bank to pay/honour
03. if issuing bank plays the role of the nominated bank, then who "nominated" it ?

In my opinion,

01. A nominated bank can honor when the credit is available with it, which is indicated in field 41A of L/C (MT 700 LC format). For example, 41A: Available with any bank by payment. In that case, any bank can honor this LC.

02. When the nominated bank has honored a complying presentation, the issuing bank will have to reimburse that bank, so the issuing bank tends to choose its agent as the nominated bank.

03. The issuing bank is the last resort where the nominated bank failed to perform either reluctant to perform on issuing bank’s instruction or agreeing to perform but later decline. It actually has more responsibility than the nominated bank.

In my opinion,
01. A bank can honor when the credit is available with it, which is indicated in 41A field in L/C