Trying to combine 3 irules together or look for a better way to execute

After each HTTP response or redirect, you must use the "event disable" function to mitigate the TCL violation of multiple redirect/response actions per request. Add the "event disable" function to your iRule1 and iRule3. For clarity, also add the "event disable" function after the "drop" function in your iRule2 to prevent the possibility of action override by another iRule.

Another recommendation is to replace "matchclass" function with "class match" in iRule1. The first function despite working as intended is obsolete.

[class match [IP::remote_addr] equals "abc_allow_dg" ]

iRule priorities

My personal observation is that a maintenance page iRule should take precedence over any security-related iRule (iRule1 and iRule2). Use the priority function "priority 100" for iRule3, use "priority 200" for iRule1 and "priority 300" for iRule2. In regards to iRule2 and iRule3, you may reverse the execution order, it's not as important.