As the others say ... only use ONE router.
However, on 2, 3 & 4, if you can turn off DHCP and give each ex-router a fixed IP address say xxx.xxx.xxx.12, 13 & 14 whilst setting the DHPc range in the remaining router to xxx.xxx.xxx.32 to 223 you might get a working network. Turing off DHCP normally changes a router into a switch.
M H C
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