Depends on how it is connected flare, compression or brazed or soldered or screwed IPS or FIPS
Yes.
You could drain the line, sandcloth flux and solder it. Otherwise, see if you can get a compression fitting that would fit the copper tubing
By the use of Flagg Flow T.P Fitting adapters and Cx M or C x F adapters attached to the T.P fitting T.P = threadless pipe
Swift Refrigerator Line was created in 1875.
Western Refrigerator Line was created in 1923.
Armour Refrigerator Line was created in 1883.
North Western Refrigerator Line was created in 1924.
If it is leaking at a fitting, it is either a bad flare or it isn't tight enough. Gas or flare fittings should be put together dry, Do no use pipe dope because this can cause a leak between the mating surfaces. If it is in the line itself, either replace the line or cut it, flare the ends and put a fitting in.
When soft copper tubing is used the end is flared so that it can seal against the fittings. A flaring tool is used to spread the end of the tubing so that it looks like a small funnel. When you tighten the nut onto a fitting it compresses the copper against the flare on the fitting and makes a seal. It is a dry seal, no pipe dope should be used on a flare fitting. This is almost always on a gas line of some sort, air, natural gas, propane or some other gas. It can be used for liquids, but generally isn't.
NO!
No, you cannot join copper and galvy directly. A brass fitting needs to be between the two to prevent electrolysis. You could also use a special type of union that has a gasket between the two halves. It is called a Dielectric union. If this junction is between pipes on your water heater and the cold water supply line, you could use a fitting made for that that also is a back flow preventer (ie a check valve).
Replace the fitting.