In addition to, if you are shooting still life, you can use several table lamps and a tripod. If you want to shoot portrait, the more lightings the better and increase your iso. Just understand about lighting and you get good quality pictures.
Flashlights can be used to light certain types of shots, but they're not generally considered a photographic tool. That said, there are many ways to light different shots, so if you give us an idea of what you want to do, we may be able to suggest a budget-friendly alternative.
No. Maybe...I wouldn't want to carrying around my Dynalites and VML to light my way around the house in the event of a power outage. My LEF Lenser works well enough for that.
For the most part no. Look, there are some kinds of shots where you want only ambient light. Or candles. Or reflection off of a wall. And if you have a good tripod and you're shooting objects that aren't moving (like products or still-life) than you can expose for 2-3 seconds. But I assume you asked this question b/c you're not looking at those situations, you're looking at shooting portraits or working indoors.
The cheapest DIY indoor lighting situation I can recommend is to go to Home Depot and get a halogen work lamp set. Two of them plus a stand. You'll need an outlet to plug them in. You'll also need an old sheet to hang up between the lights and your subject (otherwise you'll get lots of glare and hotspots. But those babies will generate a lot of direct, hard light that will beat 100 flashlights. Total setup will cost you about $35 (that's if you buy two of the work lamps and the stand plus a tarp/drop cloth at Home Depot to use instead of an old sheet). It will generate a ton of heat and if you touch the light surface you can get burned.
It boils down to light power and the time frame the light power is delivered over (duration).
A flashlight does not produce a lot of light power and it is a constant light source that delivers all its power over a period of time considered a long time in photography = like 1 second. 1 watt = 1 joule of light power in 1 second. So you will need to use long exposures and 'light painting' techniques to build up enough light for a photograph.
Camera built in flash units at full power also don't have a lot of power, but because they are strobe lights they deliver all of their power in a very shot period of time - say 1/800 to 1/1000 of a second.
Camera hot shoe flash units have even more power than a built in flash also delivered over a short time duration.
Beyond that is studio strobes that have even more power.
Quite a few of the entry level studio strobes cost quite a bit less than camera maker hot shoe flash units, but have more power.
There's certainly nothing wrong with using a flashlight and a make shift softbox for lighting - your white balance will likely be way off, but who cares. We live in the age of RAW and non destructive post production. Power will be your major heel. I struggle to get enough power even with high powered speedlites if I'm shooting in a daylight situation.
For those who are interested in cheap alternative, here is my lighting setup. That is back in the days when I was young and naive. Always setup this in your garage with a fire extinguisher. Don't do that in your bedroom or in the kitchen. These lamps can catch fire once contact with fabrics like carpet and drapery. Not safe for portrait shooting, seriously!