Update load-balancer-test-frontend-reachability.md

Added a new limitation for ICMP support and fix grammar

Author: cburuzie

articles/load-balancer/load-balancer-test-frontend-reachability.md

@@ -112,7 +112,7 @@ This section describes how to test reachability of a standard public load balanc
     | **Source** | Enter **Any** |
     | **Source port ranges** | Enter **\*** |
     | **Destination** | Enter **Any** |
-    | **Service** | Ender **Custom** |
+    | **Service** | Enter **Custom** |
     | **Destination port ranges** | Enter **\*** |
     | **Protocol** | Select **ICMP** |
     | **Action** | Select **Allow** |
@@ -212,7 +212,8 @@ Based on the current health probe state of your backend instances, you receive d
 - ICMP pings can't be disabled and are allowed by default on Standard Public Load Balancers.
 - ICMP pings with packet sizes larger than 64 bytes will be dropped, leading to timeouts.
 - Outbound ICMP pings are not supported on a Standard Load Balancer.
-- ICMP pings are not support on Global or Gateway Load Balancers. 
+- ICMP pings are not supported on Global or Gateway Load Balancers.
+- ICMP pings are not supported for regional load balancers (load balancers that are deployed behind a Global Load Balancer). 
 
 > [!NOTE]
 > ICMP ping requests are not sent to the backend instances; they are handled by the Load Balancer.