Upgrade version from 1.9 to 2.0 with custom code.

We are using nopCommerce version 1.90 for project. we are going to upgrade version from 1.9 to 2.0 for project.

can you help me to following queries,
1. How to upgrade 1.9 code to 2.0 code, we have added lot of custom code functionality in nopCommerce source code?
2. How to upgrade SQL server database? we have added new custom tables for custom code and also added new columns in existing nopCommerce tables.
3. Currently, we are using 1.9 version code which is in pure asp.net but 2.0 version code is in asp.net MVC. so please suggest how to upgrade it. Do I merge both code or replace 2.0 code on 1.9 code. please explain in detail.
4. Currently, We have integrated umbracco CMS tool with nopCommerce. if i upgrade nopcommerce then any possibility to break umbracco code due to nopCommerce upgrade process.
5. How to import data in database after finish 2.0 version upgrading task.

Please let me know if you need additional details.

Thanks,
Prafull Pokale