If you are talking about Aspose.Cells library, well, Aspose.Cells does not provide any relevant interface or events etc, you have to do it by yourself. If you are talking about Aspose.Cells.GridWeb control or Aspose.Cells.GridDesktop control, yes they do provide UI (Excel like Grid) for the users, where users can manage Excel files (read/manipulate/Save) in WYSIWYG (visual) manner.
2) Aspose.Cells.GridWeb will fit your needs here, it does also support client side functionality. See the demos and docs:
3) No, it does not support to create/manage or execute Macros or VBA codes. Only Aspose.Cells library does support to preserve vbas and macros in the template file and resave the file with it.
4) Aspose.Cells does support almost all the features. Aspose.Cells.GridDesktop and Aspose.Cells.GridWeb support the most wanted features in Excel. See the docs and demos for complete reference: