It's all threaded pipe from what I can see. You cannot just cut galvanized and reconnect with a sharkbite because of the outside diameter. Sure the IPS is all the same but the sharkbite has an ops that is less than galvanized line. Secondly they are not designed for galvanized line.you can get a female 1/2" threaded to sharkbite and screw the thread into your existing line and then convert the rest to copper or pex, but at some point it appears you need a threaded connection along the way. The only way you can cut a pipe and use a sharkbite is on copper or pex.

I think you need a plumber at this point.

The other question here is how are you going to shutoff to make these changes? The t you want to move is below your working shutoff. If this is an apartment I'm not sure you'll be able to do the shutoff further down the line and not affect your neighbors.