typically, what are the tools that u will need to do these stuff? .. that is, adding more RAM. from what i gather, we must have excellent de-soldering and soldering skills to do so?

are there multiple methods to do it? where can I find tutorials on how to solder on new RAMs?

lastly, i do not understand.. what is the issue that is limiting us from adding alot of memory? why can't the router detect properly / function as it should if the RAM used is too large?