however的用法困惑

着急的请教however的相关问题：

1，记得在element of style 上看到说，however 在某个时候不能用于句首，真有这样的时候么？我觉得ETS似乎不这么认为，但不肯定。

2， LONGMAN 上对however 作副词时的一个解释：used to say that it does not matter how big, good, serious etc something is because it will not change a situation in any way

＝  no matter how

这没问题，但请看紧接的两个例句：
You should report any incident, however serious or minor it is

.We'll have to finish the job, however long it takes.

这不是明显得run-on 句子么？ however 是副词，没有连词，逗号连接两个句子!

盼复，谢谢！

是的，谢谢！ 我明白了，however 可随便用在哪里，可是这个我还是不明白！

这是LONGMAN上的例句：
You should report any incident, however serious or minor it is

.We'll have to finish the job, however long it takes.

这不是明显得run-on 句子么？ however 是副词，没有连词，逗号连接两个句子!

这里是一个专门的 用法:

however +adj.=no matter how +adj

We'll have to finish the job, however long it takes=no matter how long it takes.

类似的还有whatever=no matter what,etc.

whatever you do,I will be here waiting for you.哈哈,好像是一首LOVE SONGL里的歌词。