There is a putty Telnet client and also a role in Windows system you can add for a Telnet client baked into the cli

Depends on the game and how the mods work. I just did a bunch of mods on Morrowwind and there was a tool for it and it was straight forward. GTA IV was super straightforward loading the mods I thought. Dolphin game mods I thought where a little funky till I spent a little time with it and was like oh this makes sense they way they are doing it and I was being a dummy not fully reading the instructions