Update magento to latest version, but keep design and products,category, orders etc. identical

I'm looking to have someone update my Magento platform to the latest version (2.4.5). I need this done as soon as possible, but with care to ensure that the design, products, categories, orders, and other settings remain identical once the upgrade is complete. In addition, I require additional custom development for the back-end. Furthermore, I need the upgrade to be tested and launched according to specific requirements, which will include automated tests. If possible, I would appreciate any advice or experience that can be provided in this process. Thank you in advance.