Comprehensive Event Management Software Development

I'm looking for a robust event management software solution that can handle both onsite and online events. The software should be compatible with Windows, Mac OS, and Linux platforms.

Key Features:
- Bulk registration
- Integration with WhatsApp, email, and SMS
- Registration, ticket generation, and QR code generation
- Attendee management including check-in system, ticket generation, QR code generation, payment processing (cash and offline with receipts), guest hotel management (including hotel and room assignments), transport and luggage management
- Event flow management and feedback collection
- Option for an event app with white-label functionality

If you already have similar software developed, I'm open to purchasing it along with the source code.

Ideal skills and experience:
- Expertise in software development for event management
- Strong integration capabilities with communication platforms
- Experience in cross-platform compatibility
- Familiarity with attendee management systems

Please provide examples of previous work and any relevant experience.