What’s the difference?

How is 「お茶でも飲んでいきませんか」 different from 「お茶で飲みに行きませんか」?

The difference is that the former is correct and the latter is incorrect.

Oops, typo error. 「お茶でも飲みに行きませんか。」 is wrong?

「お茶でも飲んでいきませんか」
Wouldn't you like to stay/stop over to have tea (before you/we go)?

「お茶でも飲みに行きませんか。」
Wouldn't you like to go out to have tea?

- "nonde ikimasen ka?" would be, for example, you have a visitor in your office, and before the visitor leaves, you ask, oh, wouldn't you stay (before you go) to have a cup of tea? Or the two of you just came out of a cinema watching a movie, then you ask your friend that question "wouldn't you like to stop over to have tea (before you go)?" It's almost like "nonde (kara) ikimasen ka," meaning "have tea" then "go."

- "nomi ni ikimasen ka?" is you are asking if the other person would like to GO for the purpose of having tea. "...(verb) ni iku" is "go (for the purpose of doing something)."

Oh, I see. Thanks for the explanation.

With 「お茶でも飲みに行きませんか」, the speaker is suggesting both going and drinking.
「お茶でも飲みに行きませんか ?」:
"Shall we / Why don't you go and drink tea (or something)?" /
"Shall we / Why don't you go for drinking tea (or something)?"

In 「お茶でも飲んで行きませんか」, the first verb 飲む (drink) weighs more in meaning than the second verb 行く (go).
The speaker is suggesting that you drink tea (or something), not suggesting that you drink tea and go away.
飲んでいく literally means "drink and then go" but practically means "drink before leaving" or so.
「お茶でも飲んで行きませんか ?」:
"Why don't you have tea (or something) before leaving here?"

Another example
「日本を去る前に連絡先を書いて行きなさい。」:
"Write down your contact address before leaving Japan."
.... 行く practically means almost nothing, while去る前に means "before leaving."
cf.
「そのボートをこいで行きなさい。」:
- "Go advance rowing the boat."
.... 行く weighs much in meaning.

//

"日本を去る前に連絡先を書いて行きなさい" and
"そのボートをこいで行きなさい" sound demanding and ordering unless an adult talking (down) to a child.

Have taken note of the point. Thanks.

I am curious if the following are all mean must?

なけばならない
なければいけない
なければならない
なければならぬ
なければなりません
ねばならない
ねばならぬ
ねばなりません

Also, I noticed a lot of kanji have different readings ye they refer to the same thing like

へみ
へび
くちなわ

Under which circumstances should we use each one?

The first one must have been a typo - but yes all others mean "must (do something)"

･･･なければ　いけない
・・・なければ　ならない
・・・なければ　ならぬ
・・・なければ　なりません
・・・ねば　ならない
・・・ねば　ならぬ
・・・ねば　なりません

The way "must (do...)" is expressed in Japanese, literally, is "if you don't do (something), it is no go."

・・・なければ・・・ねば is the "if you don't..." part, and いけない、ならない、ならぬ、なりません (the last one is polite form of ならない actually) is the "it is no go" part.

I have never seen the word "hemi" and "kuchinawa," and had to look them up in my J - J dictionary. The standard Japanese word to use is "hebi" for snake. Other words (what you refer to as different readings) are dialect words or variants used in some regions, as it seems. It is not really "different readings for the same kanji," but different words.

Thanks AK. :)

This may get a little off topic but...

Just wondering, if different regions in Japanese uses a particular reading for certain thing, would they know what each other are referring to?...

jch02140,

It's not "reading," but it's a different word :) And it's not that each region has different words for everything, nor is it that everyone uses dialect words.

So... since I didn't know the word "hemi" or "kuchinawa," if I (I'm from Tokyo) visit a farm in rural Kyushu, for example, and the senior owner there tells me "Hatake ni hemi ga ita" ("There was "hemi" in the field"), then I would ask "Hemi?" and probably the guy would say "Aaa, hebi, da." (ahhh, "hebi" I mean). With people who speak with strong dialects, I would need a bit of deciphering - some accents are heavy that I have difficulty understanding the real locals - but that's the same with every language, isn't it? :)