Only if the old battery is defective
If the car has a bad battery the battery will not charge just becaus you put a new alternator in try raplacing the old battery.
Not likely, but running the engine with a dead battery can damage some alternators. Always fully charge the battery when installing an alternator.
My advice is to charge the battery with a battery charger before starting the engine. You will be putting a heavy load on the alternator if you allow it to charge a dead battery. This could damage the alternator.
It could be the starter in it. It may be weak or need replaced.
An alternator is designed to keep a fully charged battery at peak level. It is not designed to charge a dead battery. Installing a new alternator on a car with a dead battery can in some cases ruin the new alternator. Fully charge the dead battery before starting the engine.
Kills alternator? don't you mean kills battery? Installing a new alternator without first charging the battery well (2amp for 8hrs) will quite likely burn up a new alternator as well as being hard on the battery.
is your battery Low or poor?? Charge your battery on slow charge for 8hrs to give it a good deep charge, Installing an alternator on a low or dead battery will ruin it and also not charge your battery properly.. An alternator is not a battery charger its a battery maintainer!!
Every time you disconnect a battery cable you have to reprogram the radio stations ( if that's what you are asking )
As long as the battery is fully charged it will start no matter the condition of the alternator. Eventually the battery will run down if the alternator is not keeping it charged.
see this link How_can_you_tell_if_it's_your_battery_or_alternator_that's_bad
you need a new alternator
Disconnect the batery cable from the battery while the vehicle is running, if it dies, you need a new alternator there, buddy.