You could answer these questions yourself if you did.

1 - plug in a keyboard, open ubuntusoftware center or synaptic package manager
................ in the search bar type - onscreen keyboard
choose 1 of the 4 to choose from........... install

2 if ubuntu is starting then you have the default file structure of ubuntu linux
- google search it

3 just open a folder to view and use files...click view and then hidden files
and all you config files under /home will appear ( so this answers 2
)........to view config files, logs etc you have - terminal and then Gedit is
used to edit them

4If Ubuntu is starting and ubuntu was installed on hdd - then Yes grub is
installed

5 libre office is a fork of open office and they do all the same things
........ so yes you can save as .doc file .........google search it



mate listen do yourself a favour and join some linux forums

ububtuforums.org this is the BIG one

https://www.ultimateeditionoz.com/forum/index.php
Linuxmint
BohdiLinux all have good forums and tableeeet info

then there are Android Forums and

the number 1 rule in the linux world is GOOGLE IS YOUR BEST FRIEND

So always search before asking your questions

i simply googled the name of your tablet.... Intel Exopc tablet...........oh
looky here what NO1 search result was
appdeveloper.intel.com/.../creating-multi-boot-exopc-ta\
blet

linux geeks HATE laziness ..................you could easily have answered all
those questions yourself or with a simple google search