When you are trying to improve an existing product, you first need to figure out what the existing part is doing. This is going to be incredibly difficult because you do not have access to the original documentation. Often it involves proprietary parts for which zero documentation is publicly available, and you are going to need quite expensive tooling to figure out what it is doing without those docs.
In general I do not really think this is viable to a beginner for anything beyond completely trivial product. A microwave is a really bad idea due to the voltages and currents involved (you can easily end up killing yourself). A TV remote is probably doable, but mostly because you can do that without opening up the remote at all and just need to look at the (often standardized) IR signals coming out.
When you are trying to improve an existing product, you first need to figure out what the existing part is doing. This is going to be incredibly difficult because you do not have access to the original documentation. Often it involves proprietary parts for which zero documentation is publicly available, and you are going to need quite expensive tooling to figure out what it is doing without those docs.
In general I do not really think this is viable to a beginner for anything beyond completely trivial product. A microwave is a really bad idea due to the voltages and currents involved (you can easily end up killing yourself). A TV remote is probably doable, but mostly because you can do that without opening up the remote at all and just need to look at the (often standardized) IR signals coming out.