how to create webapp using sapui5?

Hello Folks,

                  I have  an business idea and i want to convert into app using sapui5 .Actually it is my personal idea that why i just want to know following queries?

1) should i use opensapui5?

2) how will i get server access for data?

3) what database should i use?Will sapHana is accessible?

4) any other things which i have to take care?

Thanks,

Ripu