Android : i want my sqlitedb and my website to be in sync

I have SQL server 2012, Website and Android Mobile App.

In my database, I have ~20 tables and some table contains ~lacs of rows.

· I need to store all those details in my SQLiteDB . (so that i can show it even when the device is offline)

· If I update through website, that needs to reflect in my mobile db if I am in online automatically.

· The details i entered in my mobile during offline should reflect in my website automatically when i come to online.

· I want the mobile and the website needs to be sync all the time.

· when the device is always online, syncing process should take place only if there is any data update in mobile or website.

· If i enter a entry which will be consisting of ten records in it , it will be stored in 4 tables. I will save the first two records in my first table after that i will get the id of the entry, and save the remaining records in other three different tables with the id of the first table. This process needs to be done while the syncing process.

Which will be the best method for me to go ahead with that suits my requirement i'm ready to go with the paid service if required. it will be nice if i can use the proven methods like dropbox sync or amazon webservice,etc (i'm aware of these but doesn't know whether these can help me)

I'm looking for a serious answers so that i can implement it on my big process immediately.

Please help experts! Thanks in advance! :)