(PHP) Allowing and banning access to the site for different types of users and devices

There is an online store (on Vamshop) that works only in certain periods of time of day ("working" time is exposed-to-the-site). The stores website has a PHP script (we will give access to the executor). The script determines the time of the visit, the IP address (there are "black" and "white" lists of IP addresses), the type of device (search engine bot, stationary computers and laptops, tablets, mobile phones) and based on this data the crypt either lets the user to the site, or does not miss (displays static HTML stub or error 404). The script works, but with some complaints (sometimes for some reason misses the user from the mobile phone from the 4G network, although at the same time blocks it from the home Wi-Fi network).

WE NEED:

A specialist in PHP, familiar with the solution of such problems, with this area, who will be able to understand this our script and correct it, make it work as it should, perfectly. You also need to make sure that when you come in from IP addresses from the third list (lets call it conditionally "red list") the site becomes ALL not available to either PC users or users of mobile devices for a while (say, 15 minutes) after which automatically returned to work again.

Details will be provided to the chosen performer