It's not required but is usually used to weed out most people that don't give (thus are level 0), which also includes a swarm of bots, rulesbreakers or other headaches some of us don't wish to deal with.

Not saying higher levels cannot break rules (sadly) but it's less likely than the 0-1 crowd.

That depends only on you, and on what kind of people you want to give your game to.
It is usually considered that level 0 and 1 is mainly leechers or bots, with those chances decreasing with an increase in level, but it could also be poor people or young ones (therefore without a credit card) that simply cannot purchase something to give back and level up.
Also consider that the opposite is also true, since the higher the level of someone, the bigger the chances they can afford to buy what you're giving away are.

Basically there's not a right answer to your question, it all depends on your own choice.

Okay, try again. I changed key. Please work lol

Thank you :)