Permissible and Impermissible employment

Working in a grocery store that sells haraam meat and alcohol

Q: I wonder if it is allowed to work in a grocery store. You need stock up shelves with pig and haram meat and also halal products such as bread, fruit and clothes. You need to stand at the till and scan the goods for the customers (cashier). It is approximately 90% halal goods, but also goods such as cigarettes, haram meat and alcohol may occur. I wonder if I can work in this place.

Producing ads for people

Q: Is it permissible if I start a business doing ads for people? As far as I understand, the ad is digital and does not physically exist. If I stipulate the condition that you are paying for the service of making the ad will it be permissible? 

What is also the ruling regarding buying something, like an ad which is digital, as it doesn't physically exist and qabtha cannot be done?

Taking a salary from a person who took out an interest-bearing loan

Q: I am a student. I teach my aunts son mathematics. This is my first job as a student. I always wanted to earn halaal or I have a wish that my first salary or income will be atleast halaal.

My question is, somehow, I know that my aunts source of income comes from riba or a bank loan or something or fraudness which is haraam. Is my salary halaal or haraam? I am confused. Please explain, if it is not halaal then I will teach him for free. 

Working online under someone else's name and profile

Q: My sister recently applied for a tutoring job with good payment online. However, due to being occupied with household chores, she asked me to tutor the kids under her name and profile (without the one who hired knowing) since I am looking for a tutoring online job too. I'm not as qualified as her although I'm qualified enough to tutor those kids but I refused thinking that it would be a deception. Was this act permissible?

Earning from delivering food with Uber Eats etc.

Q:

1. Is earning from food delivery (Uber Eats, deliveroo, etc.) halaal, when most of the food delivered is not halaal?

2. What's the ruling on haraam earning in the past which a person didn't have knowledge at the time of earning but when he got to know its haraam he stopped that source of earning? Is the haraam earning in the past permissible to keep, even when he didn't have knowledge of it as haraam?