Yes, postage is determined by weight category, not envelope size. Everything that weighs one ounce or less falls into the same weight category.
yes
The same as a standard A4 envelope ... 44 cents. There is only a price break for postcards. If it's any kind of envelope, that can be sealed, it requires first class postage.
If a political candidate sends along a return envelope marked "no postage necessary" then mark in bold letters a request to remove your name and address from his/her mailing list and return it to their mailing address. They pay the postage. If the return envelope has no postage paid for return then mark the letter the same way and return it postage unpaid anyway. Make sure your name and address are not printed on the back of the return envelope. If so, throw it in the trash.
When addressing a side flapped envelope the side flap should be to to the right - regardless as to whether the person is addressing the envelope is left or right handed. So the postage stamp is on the same side as the opening flap.
Yes, it is the same for the same weight. Both are considered 'oversized' mail or 'flats' and cost more than a normal business envelope. the current rate would be 88 cents for the first ounce and 17 cents for each additional ounce.
It all depends on the envelope size. A standard flat envelope is about $1.00 while a larger flat envelope is about $1.24. I had the same question and found my answer here: http://postcalc.usps.gov/
It depends on the weight of the envelope and where you are sending it to. In general, a manila envelope with two papers may require 2-3 regular stamps for domestic shipment within the same country. It's best to check with your local postal service for specific requirements.
The same as you would a short envelope.
$0.98 for a standard letter size envelope weighing up to 1 ounce, United States to Germany. It's the same rate to all USPS "Group 5" Western European countries. Source: www.usps.com
Hawai'i is part of the United States, therefore the postage is the same as it would be to or from any other US state if you are using the USPS.
Nothing, really. Most mail is assumed to be sent First class, which is the standard or regular mail. If you are sending merchandise, you can reduce the cost, but it will not get certain priority handling. There are many different rates that can be used in bulk mailing, but First Class is usually going to be your best bet.
Just one. Post cards and regular First Class postage is the same for Alaska and Hawaii as for the contiguous states.