Question on gdb integration flow in vscode for C++ application on Linux

I moved from emacs to VS Code few months back. We have a large C++ code base. In emacs, I used to debug using gud-gdb interface. However, I have not been able to successfully setup gdb with vs code.

I just want gdb to get launched and load the binary (not start the run). This is because, I have gdb python script that I use to setup PATH and LD_LIBRARY_PATH depending upon MYPROG_HOME env variables and I want to use that as well set args before running the program.

I have tried following launch.json -

{
    "version": "0.2.0",
    "configurations": [

        {
            "name": "GDB Debug Manual Mode",
            "type": "cppdbg",
            "request": "launch",
            // "program": "${BUILD_PATH}/bin-linux64/myprog-G",
            "program": <full-path to myprog-G>,
            "cwd": "<test dir where I want to debug>",
            "MIMode": "gdb",
            "miDebuggerPath": "<path to gdb>",
            "stopAtEntry": true,
            "launchCompleteCommand": "None",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                },
            ]
        }

    ]
}

But when I invoke gdb from the Run and Debug option, gdb prompt comes up. But when I try any gdb commands (like show env MYPROG_HOME), it gives me below error message:

Unable to perform this action because the process is running.

Waiting for longer time (5-10 min) does not help. I must be missing something. Can somebody guide me what am I missing or how to debug it further to understand the issue?

I am using gdb 14.2 version (cannot override this to newer version as we cannot install a new version).

Edit 2 (after edit by another user):

I tried enabling logging using following:

            "logging": {
                "engineLogging": true,
                "trace": true,
                "traceResponse": true,

            },

And now when the gdb prompt comes, if I type "show env PATH", I get following o/p -

show env PATH
<--   C (evaluate-25): {"command":"evaluate","arguments":{"expression":"show env PATH","context":"repl"},"type":"request","seq":25}
--> R (evaluate-25): {"type":"response","request_seq":25,"success":false,"command":"evaluate","message":"Failed to handle EvaluateRequest","body":{"error":{"id":1105,"format":"Unable to perform this action because the process is running."}},"seq":215}
Unable to perform this action because the process is running.

Does it mean "stopAtEntry" : true not working for some reason. Is it possible to specify to break at main?