Yes, because all of the hair products that have been used on the dolls hair goes into a hard type of glue also it could really damage the dolls hair. So its best to not do it.
Mattel made Monster High dolls also they made Barbie , Hot Wheels , etc.
Half No, You can not straighten a dolls hair with a straightening iron but you can boil wash it straight.
You can find Monster High dolls in Target, Toys R Us, or online, like eBay or Amazon. Hope this helps :)
You put them on the computer at monster high.com or on the sweet 1600 app on i-pod or i-phone