[Sashimister]

Originally Posted by pacerier

if i use [V]ては(いけない/だめ/ならない), does it sound stronger compared to using conditionals to express "you must do X"? e.g.

I'm not understanding your question, to be honest.

(1) 夜、遅くまで電話してはならない
(2) 夜、遅くまで電話しないとならない
(3) 夜、遅くまで電話しなければならない
can we say that (1) is more authoratitive than (2) and (3)?

That's hard to answer when the sentences don't even mean the same and one of them (2) makes no sense. (1) and (3) have the same in the degree of authority.

Also, if the meaning of と does not apply here, what will be the difference in naunce between (2) and (3).

Again, we don't say (2), so it's impossible to talk about the difference in nuance. I don't know what (2) means.

Also can たら conditional be used in this way: 夜、遅くまで電話したらならない

Nope. That will be しては.　　Seriously, where are you getting these incorrect phrases?

As for 「ば」 conditional and 「たら」 conditional, is it true that 「ば」 focuses more on the left part of the sentence, whereas 「たら」 emphasises more on the right part of the sentence?

Not really. However, this is possible in speaking, if not in writing, because in speaking, you can stress any word you want and as much as you want. In writing, you never know which word the reader will give the emphasis.

Originally Posted by pacerier

Heys all again, sry for another question, i've read somewhere that the particle から when used to mean “lowest extents: prices, business hours” can be replaced with より. I was wondering if this is a common practice i.e. will this sound weird:
我々は7時より営業して居ります。

That is a very common practice. 　から sounds less formal than より.

But your sentence sounds weird for two reasons:
1. We don't address ourselves 我々to our customers.
2. Good writers don't write おります using a kanji.

Just say 7時より営業しております or 7時より営業いたします.