How to secure a network using ARP

RouterOS Beginner Basics
1

I folow this tutorial.

https://wiki.mikrotik.com/wiki/How_to_secure_a_network_using_ARP
I have the hEX RB750Gr3 with RouterOs 6.43.4 with default configuration.
I want secure a network using ARP

Why does the ARP configuration come in red? can is set the ARP settings per port? If I allow the laptop via static ARP, this line will be in red.
And I remain a dynamic ARP.
What is the problem ether 2 to 5 standing in the bridge.

/interface bridge
add admin-mac=xx:xx:xx:xx:xx:xx auto-mac=no comment=defconf name=bridge
/interface ethernet
set [ find default-name=ether2 ] arp=reply-only

who can help me

2

if some interfaces are bridged / switched they are part of same broadcast domain = what one interfaces will see is same as the other.

In such a case, arp should be controlled on the bridge level.