begin变 ing 形式要双写N么 还有 动词的ING形式都什么时候双写N？

不用，现在分词，一般进行时，动名词做主语时
还有时是固定句型
Keep doing
have fun doing
think about doing
what about doing
do well in doing
enjoy doing
be good at doing
finish doing
be busy doing
practice doing
as for doing
the way of doing

双写N都有：
swimming
running
shopping

不需要 单音节如果最后一个字母发辅音 双写最后一个字母

begin要双写。因为最后字幕双写的原则是：闭音节以一个辅音字幕结尾，该辅音字母双写。比如，put, cut, forget.

当然要~
双写N的情况：辅音字母前有个元音字母就要双写~