The CPU is bounded to the Touch ID, so CPU cannot be changed. The ram can freely change.
I am sure DIY is different altogether. Watching is fun. Doing is another.
I can say, with the underfill of the CPU below, installing the RAM above with application of hot air will be a huge huge challenge. Chances, are some of the lines will be shorted
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Many iphone repair men will quickly not accept jobs of PMIC, CPU job, water damage jobs. Touch problem, VCC main etc.... they will grab.