I am amateur/barely novice to home networking trying to narrow down, if at all possible, angles of intrusion.
Attacker connects to home network after I willingly give password. Before they connect I:
disconnect my pc (laptop Windows 10) from home network but leave my phone (Oneplus up-to-date android) connected for duration of their stay.
I turn off access to administration for router (Huawei HG8145V5) from WAN side and LAN wifi side and change default ip for getting to administration login page to ip outside of range of "rented" ip addresses and put long powerful password
unchecked all ips in router administration whitelist (probably remote assistance ips from isp since router was provided by them)
Attackers leaves and I factory reset the router (I restored same security settings) and my phone. Under these conditions is it still easy for the attacker from outside the network to put spyware that allows my monitor's contents to be seen ("system monitor" type of spyware?) on my pc and/or phone and that is resistant to factory resets of said pc and phone?