Wanting some job offer advice...

I have no idea for any of the questions, but you should just interview to use it as practice for future job interviews.

It never hurts to try. Going on the interview doesn't mean that you have to take the job. At least you'll know everything about it and it'll be easier to decide.

Insurance sales? Yeah, most likely a call center.

Not the most fun job. Often times pretty stressing. You usually get little to no rest between calls and the way some companies set it up, you'd be surprised that their offices haven't been put on fire by their employees.

Yes. No. Maybe. Who knows.

Might as well head on over to the interview or ask all you can beforehand.

I don't have personal experience with that line of work, but my partner kinda does. He has worked many sales jobs and although none were directly related to insurance (that I can remember) a lot of sales jobs seem to be similar.

Job ads can be downright sneaky sometimes and if they don't directly answer a question in the ad (Like what exactly you do, whether it is cold calling or a kiosk in a mall or whatever) then I would probably assume the worst and say yeah, it probably is a cold-calling type of job. A lot of sales jobs are that, but that doesn't stop them being good job opportunities. What I would look out for is whether or not it is commission based work. A lot of sales jobs advertise their potential to net you commission bonuses, and that's fine, but re-read the ads carefully and don't take a job where it's 100% commission based. You can be the best salesman ever and convince heaps of people to get insurance, but the bottom line is that if they don't need or want it, they won't buy it, and you don't want other people's decision to buy or not buy your product to directly influence how much money you make. Job security isn't worth squat if you can't make enough money to put food on the table. I would much rather earn a lesser, steady wage than one which fluctuates week to week.

My partner is honestly excellent at sales. Being around him when he is on the phone has taught me a lot about what makes a good salesperson. He has a great phone demeanour and is very well spoken, he is polite, listens to the customer's needs and doesn't pressure them into making decisions. I think its a job you need a lot of patience for and you need to know your product back to front and inside out so that you never miss an opportunity to relate a benefit of the product to the customer's situation. (ie 'My phone is old and outdated, if it breaks I would rather buy a new one than have it repaired under your insurance' 'Well with x type of insurance you can actually get your old phone replaced with a new one of your choice for only x dollars extra per month')

I'm not sure it would be a super fun job, but for the right people and with the right company, I definitely think it can be rewarding. You obviously have quite a lot of experience in customer service, so it probably wouldn't be hard for you to make the transition into phone sales, as long as you're confident on the phone. Plus a phone job would be pretty good for you since you have a back injury, you'd get to sit down all day instead of walking around lifting stuff.

I really cant tell you anything for first 3 questions, but for 4th may have some input.
In theory they can blacklist you, but if they would do that with everyone who refuses their offer they would end up without possible future new employees. Most companies keep record all CVs they get, just for future, especially if the market for that profession is demanding.
If you are unsure try getting short term contract, to get acquainted with a job. If you are able to work and you are getting bored at home, then you don't have any excuse not to try.
Maybe, wait a little to see if you get any other offers in next few days.

Also, few of my friends started working at low level jobs, as phone operators, but it was actually test from company and after 3 months they got promoted to suitable jobs.

Good luck with job hunting.

Keep in mind there are people that troll those sites to trick people into giving personal information for identity theft purposes. I'd recommend verifying the email domain is legit before doing anything.
1) Depending on the business it could be a call-center job or door-to-door. If they say work from home be suspicious. If it's a call-center job it could be cold calling but typically large businesses will have a hot list. Basically you'd be calling people that just bought a house or car and the dealer/broker sold their contact info to the market.
2) I know people that have done it. They all hated it. Some people make good money on commissions but any job dealing with selling something people don't want is stressful.
3) Not fun or rewarding. You'll be expected to meet quotas and pressured by management. I've heard horror stories so be warned.
4) Companies usually keep your info on file about 6 months. Sometimes forever despite legal requirements. If you do something that they don't like they can mark it somehow to never hire you. Sales jobs have high turnover so if you haven't worked for them yet they will probably hire you in a pinch.

It never hurts to find out more about things. But from my experience I'd be vary wary about these jobs. Sales jobs that are that easy to come by seem to generally be commission based and stressful with a high turnover. I got as far as a training course for one once and it was all about giving people the hard sell and looked awful - fortunately I never went through with it as I heard back about a much better job that I had applied for.

1) Is it something akin to cold-calling/telemarketing?

Due to them being insurance sales, it sounds it is most likely. But then again it could be door-too-door sales. With cold-call/telemarketing jobs, they don't have to specify what the job actually is as most people who apply either already know or just need a job and are not that eager to learn what it is.

2) Has anyone had experience with this type of career?

I have had experience with the interviews with these types of jobs. Most were eager to get me to work with them, even when I explained my experience isn't relative to the job. Most of the work in these careers I can say isn't too hard and are manageable. It just isn't fun or rewarding. (This is from someone who has 5 years customer service exp. and enjoys standard CS work ) But!! These jobs are different for everyone! You personally might find interest in the job and find it to be personally rewarding.

4) If I say no to the job offer after an interview, will they blacklist me from life and garnish my hard earned potato wages?

I would say no, but that depends on the industry in your area. I know where I live I have the right to turn down a job after an interview without being blacklisted (and I have done successfully and later gained better employment in the same week). I really doubt they'd blacklist you after turning down the job, after all the interview isn't one way, it's also so you can learn more about how the company runs and if it's a good fit for you as a person.

Good luck and hope you succeed :)

Those are (sometimes automated) spam offers. Ignore them

"in less than 24 hours, I received three personal job offer for insurance sales"

If you think those are legit PERSONAL offers just for you, then you may be just the kind of person they are looking for....

https://answers.yahoo.com/question/index;_ylt=A0LEVrbTFUtVzD8Acm8nnIlQ;_ylu=X3oDMTByMG04Z2o2BHNlYwNzcgRwb3MDMQRjb2xvA2JmMQR2dGlkAw--?qid=20080522220357AAuqBqT

http://www.city-data.com/forum/work-employment/731260-anyone-getting-calls-insurance-companies.html