"Te quiero" is more colloquial, more usual. At the same time, it means all kinds of love ( you can tell "te quiero" to a child, a dog, etc...). By the other side, "Te amo" it's only use with a romantic love.

"Te amo" is more compromised than "te quiero". You can say "te quiero" to a niece. You usually say "te amo" to the only one in your life.

Is the same, but "te amo" is more intense hehe

The difference lies in how much you deliveries to the person. When you loves you give all of you to the person

Yes ,they both mean 'i love you' .