＊について can replace に関して. It is less formal, though.
＊The polite form に関しまして can appear in formal speech.
＊に関する is the prenominal version of に関して and can be used to modify the noun which follows.
FORMATION: Ｎ + に関して Ｎ1 + に関する + Ｎ2
Note: As previously stated above, though this is interchangeable with について, there is a particular feeling and depth of conversational topics that に関して is used for. This is usually reserved for serious discussion topics, assignments, or "grown-up" levels of discussion, where as について has a more general usage.
最近、株に関する本がたくさん出版されています。 Recently, many books about stocks are being published.
Regarding yesterday's lemonade, I think I put in too much sugar.
In the above sentences, the first one would be seen as a more proper usage of に関して given the overall tone and "adult-ness" of the conversation. In contrast, the second sentence would benefit more from について as the depth of topics simply don't match well with the tone usually associated with に関して. To make things a bit more pictorial, imagine a 6 year old speaking with a PhD's vocabulary and vernacular, something just wouldn't seem correct about it.
I changed the title from 二関して to に関して, because it's not the kanji for "2" that is needed. The particle "ni" is needed.
In ex #5978, I think perhaps you meant この質問に関して、３つの問題がある。