1. Is it possible to create a Bootstrap theme for Ext.Net ?
2. If Yes, what are the steps required to build a theme ?
3. Once the customized theme is ready how to apply it to existing Ext.Net application ?
These threads might be helpful.
4. Are there any ready-made Metro Style themes ?
I've not seen. Though, it might exists for ExtJS, at least. If so, you could take/buy it and adjust to Ext.NET.