I have one more question.
The w120 and linksys wry 610n use a similar type of CPU as bcm47xx.
If squashfs.bin of wrt610n is installed on w120, can it be operated?
No, there is no such thing as a 'generic' version of OpenWrt for embedded targets like mips or arm. If you want to see your device to be supported by OpenWrt, you'll have to go the long way round and port it to your device properly.
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but even if you do get your device ported properly, its wireless will remain close to unusable - and that is not going to 'ever' change with Broadcom wireless.