I was wondering if I can continue using the online diary when my computer uses the 3g networking communication, instead of over wifi. In other words: will your online diary server ‘find’ my laptop when I connect to internet through 3g (or 4g).
>> I was wondering if I can continue using the online diary when my computer uses the 3g networking communication
No, this won’t work for 2 reasons :-
 your IP address will keep changing each time you connect to the 3G network and the diary won’t know where to look for your database
 even if it could connect on 3G, the performance will be so bad that it will be unworkable (see https://pioneersoftware.co.uk/forums/topic/faq-109-how-can-i-improve-performance-in-the-online-diary?view=all