What documents do I need to travel in Mexico?

Okay so here is my situation. I'm a US citizen (born in the US), however I have the option to become a dual citizen because my mom is from Mexico. I'm going to be flying on a US plane from Texas to Mexico City, then I'll be flying on a Mexican airline from Mexico City to Cancun. Do I need a visa? Or any other special documents besides a US passport? Would it be a lot easier if I get my Mexican citizenship?

Can I get alcohol in flight after alcohol distribution is over?

Should I get my complimentary alcohol only when they bring the cart to my seat? What if I need alcohol after 3 hours? Can I go up to the hostess at the back and ask? I have 10 hour long flight in jet airways economy class, so topping up my alcohol every 4 hours might help me go through long hours of travel

Added (1). My question is only about a couple of drinks. Not about spending entire flight hours inside the toilet puking. Looks like people can't wait to name and shame the other person without any proper understanding.

Flying with cigarettes in my handluggage?

I'm flying from Sweden to England tomorrow. I've been asked by my colleagues to bring cigarettes back with them since they're cheaper. I'm only taking hand luggage and won't be checking in any hold luggage, the cigarettes would already be in my handluggage when I arrive at the airport. I've checked the limits on how much tobacco I can bring into the UK before having to declare it to customs, so I won't have any problems on that end. But I'm worried that when security at the Swedish airport xray my handluggage, they will remove it from me, simply because of the sheer amount I'll have (probably 10 packets or so). I have read its permitted to bring tobacco in handluggage. But since itll be a lot, I'm just worried I'll be called out on it. Can someone clarify?