Edward's works. The edward's procedure or supercrestal fiberotomy was described in 1970 and assists in retaining problematic, rotated teeth. This small procedure is usually only accomplished for 1 or 2 teeth. The need, the process, and the risk/benefits should be discussed with your orthodontic and periodontal specialist.
Keep teeth straight. It can be a good idea if your teeth had to move a lot to be straightened. A retainer will be necessary as well.
Yes good idea. Fibers between the teeth are elastic in nature. With braces you can close the spaces and wear retainer but you need to remove cause of spaces.