Router witch Openwrt and BCM6756 transfer to other Router (3 replies)

Hello,
can you help me please.
i have a Router with Openwrt and BCM6756 and it run well.
Yes i know this is very special.
I call it Router A.

2x Router B the little brother of Router A:
I flash the Image from Router A to Router B.
Router B start the bootloader dont load the image from Nand.
And no Network and no usb
After i change the Boardid i have Network Access and usb
But i chacnge it the Bootloader to test say: Need Hard Reset. I think one die.

I have SSH and Serial Access to Router A and B.
I have MTD and Nanddump with openwrt from Router A.

Can you Help me please:
Plan 1: Router B bootloader and Router A Openwrt.
Plan 2: Router B boot from Nanddump?
Plan 3: I write the mtd (only image mtd) from Router A to Router B?
Plan 4: Usb boot Router B with Nanddump from router A.

Thankyou :-)