WhatsApp, from the month of November will no longer work on some devices that have an obsolete version of the application compared to current standards. 
The instant messaging service is periodically updated to improve the functions and commands of the application, which in turn need to be updated on the device's operating system.
For all smartphones, the application updates automatically, in fact you will not need any permission, but you will only have to follow a procedure that verifies the proven ownership of the device.
From November 1, 2021, the instant messaging application will implement a maintenance service for all versions of obsolete mobile phones, which will not be able to take advantage of the update.
The company acquired by Facebook will not update devices with the Android 4.0.3 operating system down, while on Iphone from the IOS 9 version down they will be excluded.
Here is a list of devices where no updates will be made:
Huawei: Ascend G740, Ascen Mate, Ascend D2
LG: Lucid2, Optimus F7, Optimus F5, Optimus L3 II Dual, Optimus F5, Optimus L5 II, Optimus L5 Dual, Optimus L3 II, Optimus L7 II Dual, Optimus L7 II, Optimus F6, Enact, Optimus L4 II Dual, Optimus F3, Optimus L4 II, Optimus L2 II, Optimus F3Q.
Samsung: Galaxy Trend Lite, Galaxy Trend II, Galaxy S3 mini, Galaxy Xcover 2, Galaxy Core, Galaxy Ace 2
Sony: Xperia M.
ZTE: Grand S Flex, ZTE V956, Grand X Quad V987, Grand Memo.
Otros: Archos 53 Platinum, HTC Desire 500, Caterpillar Cat B15, Wiko Cink Five, Wiko Darknight, Lenovo A820, UMi X2, Faea F1, THL W8
IOS
Apple iPhone SE (16GB, 32GB, 64GB) Apple iPhone 6S (16GB, 32GB, 64GB, 128GB) Apple iPhone 6S Plus (16GB, 32GB, 64GB, 128GB)
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WhatsApp, some devices will not be included in the latest app update
If you have one of these devices you will have to abandon the idea of updating the application, you can try to make a backup copy while looking for a new device to transfer them and download the update.
A backup copy is available on any device, this is an option of the instant messaging service, which will allow you to check all sensitive information and transfer it to another device via Bluetooth or cable.
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To activate this option, you will have to tap on Other, Chat, Security Copy. When you have to transfer all the data to another mobile phone, you must indicate the recipient telephone number of the data transmission.
In this way, if you have one of the devices not supported by the update, you can transfer the data to another electronic device, this is necessary when you need to migrate from IOS to Android and vice versa.