yes, if you lose
What is your take on elo-farming?

I play higher rated players to farm their ego
yeah, happens to me too. elo farming is basically the opposite

yes if you lose it is sandbagging when you play against a lower rated( or just purposefully give away free pieces and resign)
correct

what about using alt account to play against the main account
also farm but more effective and more getting ban

yep. i had an alt. but closed it due to email/login poblems for my main, and never played against it for that reason

The intentions of a person elo-farming will decide whether it's moral or immoral. Some players can set up matches to purposefully fight against low-rated players and gain points, doing this often is quite dishonest. However, doing it once in a while doesn't seem wrong to me either. I mean your ELO is the measure of your strength, regardless of how much you farm you'll eventually return to your true ELO rating once you're matched with stronger opponents.

The intentions of a person elo-farming will decide whether it's moral or immoral. Some players can set up matches to purposefully fight against low-rated players and gain points, doing this often is quite dishonest. However, doing it once in a while doesn't seem wrong to me either. I mean your ELO is the measure of your strength, regardless of how much you farm you'll eventually return to your true ELO rating once you're matched with stronger opponents.
Well-said, I agree with that.
For everyone that didn't know, elo-farming is where a player will play people lower rated than them to (usually) guarantee a win although gaining less elo per game. I've been asking around in person and got mixed responses. I personally believe that as long as you play at your skill at least 50% of the time (if possible), it's okay to do once in a while. Some people I've talked to have said it's okay and some say it's morally incorrect, so I was interested to see what the community thought.