do they help with hot water tank replacement
It is posible to buy a replacement stainless steel hot water tank. There are many retailers available online with competative prices to suit your needs.
Possibly your hot water tank is rusting out on the inside and will need replacement soon.
The hot water tank might be undersized for your usage.
how long does it take for hot water after lighting water tank its gas?
I assume you mean hot water tank. The hot water tank was supposed to be the most efficient way to heat your water because heat rises. Since heat rises most of the heat energy would be absorbed by the water in the tank and very little of that energy would escape through the top of the tank. However; building scientists are now saying a direct hot water heating system is more efficient than a hot water tank because in a direct system you are not heating water until you need it, so you are not heating water you won't be using. If you frequently use hot water a hot water tank is the way to go. If you rarely use hot water a direct hot water (tankless) heating system is the way to go.
No, a hot water tank heats water by itself.
So the steam can rise from the boiler to the hot water tank storage
No, a hot water tank heats water by itself.
You will get warm instead of hot water. There is a tube inside the tank on the cold side that goes to the bottom of the tank and the hot comes directly from the top. Reverse them and you are going to get the cold water that settles to the bottom of the tank. It will not hurt the tank or anything, it just makes for poor hot water.
It would help as most of the rust accumulates at the bottom of the tank.
If the hot water tank is off it is possible. It is also possible for the cold water going to the hot water tank to freeze. Insulate all pipes that are exposed - or let them drip (this is more expensive!)
it is a tank that preheats water and holds until you use it