iRule condition - request contains more than 10000 parameters

Have you tried increasing maximum parameter learn field under blocking settings? You can increase that limit. But I would suggest work with your application team and get the actual number of allowed parameters and configure that value accordingly. Alternatively, you can change parameter settings to wildcard (never learn) and it will not check the number of parameter limit.

you can make irules that split request uri to array using "&" character as splitter then use the array length as condition.

anyway, it's better to use post body rather than uri parameters for such large request data.