4wd mode is not required upto and going through Tarishing. 4wd will only be required if you plan to go up and across the Glacier. Tire pressure is as important as switching to 4wd, make sure you reduce it. Before you attempt the Glacier, do have a look and see if you want to do it. Locals might advise you against it. It is not difficult but you need to be careful.
Which city are you based in, most big cities have offroad clubs and try to join there events to learn the basics of 4wd. Do some trips with them before you go offroading by yourself.
Would recommend you watch some offroading videos, one of my personal favorite channels is https://www.youtube.com/user/RonBacardi666 . As a start, check out the following;
& this is coz of the Jimny
https://youtu.be/sBT1EGDEi0A