Hot water line. If you did hook it up to your cold water line make sure your dishwasher is set to heat the water (some models have a selectable setting for this.)
Dishwasher line is hot water. Tie ice maker into 1/2 inch cold line going to kitchen sink.
No
Yes, you can use brass fittings or the plastic fittings that snap onto to the plastic line. I like the snap on fittings.
It is where the supply line is attached to a water line. May be under the kitchen sink or in the basement under the refrigerator in the closest supply line. Should be a hot water line. Hot water because most of the minerals stay in the water heater and the water in the supply line will be cold from sitting. Someone may have put a shutoff at the floor behind the refrigerator, but I doubt it.
You need to run a new connection from the cold water supply line to the icemaker. This will probably require the services of a plumber, who will cut the cold water line upstream of the washing machine shut-off valve, add a tee, and run a new line to the refrigerator location. A shutoff valve for this line will be added, and then the line to your icemaker attached to that.
you want your cold line coming tying into both inlets on the water heaters and the hot lines tied onto the outlet side of the water heaters evenly (so they get even draw and one water heater doesen't have to work harder tnan the other). your recirc line coming in ties into the cold line in beetween the two water heaters with a circ pump going twards the cold line and the other end of the circ line tying into the hot line on the furthest fixture. on the cold line coming in you need a ball valve, check valve and expansion tank before it ties into any of the heaters. NOTE: The solution above is for tanks in parallel not in series.
only if you have an ice maker.
It should be hooked to a cold line.
The water line where it enters the ice maker could possibly be frozen.
Install on cold water line.
If you have a fishing pole, you need a line attached to the pole in order to fish. You need a hook on the end of the line. To put the hook and the line under water, you need a sinker. So, to have everything you need to fish, you need a hook, line, and sinker. The idiom means you need it to be complete.