The standalone 705 comes with a base map which is VERY basic. So to use the unit properly you need to buy or install some maps. The garmin maps are very good but expensive. You can also use some of the open streetmap maps which are getting better all the time.

It charges by USB so I'm sure you can. If you use the backlight sparingly the internal battery last quite a while.

You cannot use the device while it is charging.

Sort of.

It can show a compass that points to the next waypoint of a route you are following. You have to be moving to get a direction as there is not an actual compass in the device.

Its a bit anoying as the maps tends to jump all over the place when you stop.

Still a very good piece of kit though.

No

Garmin Mapsource is a free download and is used to trim and upload maps, routes, waypoints etc.

By trimming the maps in Mapsource you can reduce their size allowing you to store multiple maps for different occasions such as cycle route maps, ski maps, town maps etc.

You can also download Garmin Training Centre software for free but I prefer Sporttracks to analyse and view rides.

Not sure about the Trip and Waypoint software but you can edit waypoints in mapsource and/or Training Centre.

Yes. the estimated time of arrival is just a bit out!

No. The unit is sealed but has 6 screws on the back so you could probably open it up. I wouldn't recommend it as it would void any waranty.

If the battery is dead and you have no waranty then go for it. What do you have to lose?

Both, you have so many options you will be amazed. You customise screens to suit. Great device.

can not display Japanese.

You need local maps loaded, GPS works anywhere. Google Garmin GPS Maps Japan.