I'm planning to flash my 1490T EU with an alternative version...

What are the main difference between

Japanese version 2.70
Taiwan 3.30:
Philippines version 2.10:
Singapore / Malaysia version 2.80 for 1460

or I have to test each one... Also I use my Nuvi in Portuguese French or English ... will I be able to change beteween these languages after I flashed with one of this firmware

last but not least... will I be able to upgrade normally with webupdater after I done so?

thks