What questions must one ask themselves to help understand rather they are in love or in lust.?

Love and lust are synonyms. It's the result of a temporary chemical imbalance in the brain. The effects and duration are impossible to predict, with any degree of accuracy.

"Would I still feel the same about this person if they were in a terrible accident that left them scarred for life?".

Falling in love is a process which takes more than a week or a few months.... it's about growing emotionally close to someone, putting up with their quirks/accepting them at face value, respecting them and trusting them. Most couples who truly love each other treat each other decently - and usually have decent sex lives.

Lust is about sex, sexual attraction and being giddy over someone, mostly.

Love is when you can handle being with someone all the time. Lust is when you can't stand being without them

Can you picture the rest of your life with or without the person in question? Would you do anything for them? Do you just want sex? How would you feel seeing them in a relationship with someone else?