Please explain #1.
OK everyone... Let's not beat up on someone who's trying to learn safety.
Code only allows parallel wiring when they're single conductors (not bundled extension cords) and with large diameter single conductor over 1/0 that would be too cumbersome if a single larger conductor was used. See here for a pretty good explanation of when it's allowed: http://www.ecmag.com/section/systems/conductors-connected-parallel
Remember the NEC is a century long document created by a lot of engineers who want to prevent loss of life and equipment. While you "might" be able to get away with your wiring scenario and have nothing bad happen, if someone less knowledgeable were to do something silly (like use different length extension cords or plug into different phases, etc...) it could become very dangerous and possibly cause a fire, damaged equipment or even loss of life. Plus you have to consider your own liability. If you were to do something like this and a fire or death occur, then you would be on the hook for potentially millions of dollars. I assume you don't have a business and insurance, so they would come for your house, properties, car, boat, etc... It's just not worth the risk to save a few bucks. As others have noted, a heavier extension cord will reduce the voltage drop considerably. And many times I'll run a long 10 gauge extension cord 100 feet just to reduce the voltage drop, even on a 15 ampere load.
So you're not going to find anyone here on this forum who will tell you this is OK to do. It's a code violation. It's dangerous if anything goes wrong. And the personal liability could cost you your home and business.
There's also one more thing to consider that I think about a lot. If I did some sub-standard trick and someone was injured or killed, I would have to live with that guilt for the rest of my life. That's why I insist that everything is done as safely as possible, and many times we go beyond the basic code requirement since it can't account for EVERY crazy thing we have to do. The National Electrical Code is a MINIMUM requirement, and it's up to the installer and inspector to judge if it's adequate as written or you need to be even tougher on yourself. I always try to error on the side of safety.