kanji - About writing numbers using Japanese numerals vs using Arabic numerals

I noticed that even though Japanese language has kanji characters for numbers (e.g. 十、百、千、万　etc), there are many places where Arabic numerals are used instead, for example, prices for shop items are written as １００円 instead of 一百円.

I am curious about:

1. 
   

   When did Arabic numerals start replacing Japanese numerals for writing numbers for normal daily uses (e.g. price tags, signboards, phone numbers etc)?

   
   


2. 
   

   Other than writing small numbers like in dates (e.g. 十月九日), are there any places where large numbers are predominantly written using Japanese numerals (e.g. 六万五千七百二十四)?

   
   


3. 
   
   

   For places that use Arabic numerals, when there are large yet trivial numbers, for example "three hundred millions", do you still write it as 300000000, or switch back to 三億 (since it saves space)?

   
   

Answer

What I can think of is Japanese numbers are using when registration of house, family registrations, and some contracts.

But they used 壱 弐 参 拾 萬 instead of ー 二 三 十 万 on those kinds of registrations, contracts to prevent obvious modifications. And according to trade law, session 2, No. 48 「壱、弐、参、拾」 are mandatory.

Old books using those Japanese numbers a lot in (years, phone numbers, addresses, postal codes) but recent one most of them are in arabic numerals.

Here is screenshots of the Old one (Natsume Souseki「夏目漱石」's Kokoro「こころ」) and one of recent book at 2009.

Regarding big numbers like company capitalization, they may just used roman numbers of japanese units like 3億円, for example like this for this company

資本金 : 1,887億7,534万円

But for statistical data like company achievement/results data for stock share owners, they may use those numbers in long numbers like following, and they may use one Million's equivalent 百万円 Unit.

売上高 : 3,004,640 百万円