Shopify Custom Popup Form Integration with OTP & 3rd Party API Automation

I am looking for an experienced Shopify Developer to fix and complete a custom flow on my landing page (Horizon Theme). The core structure is ready, but the integration is not triggering correctly.

Key Requirements:

Custom Popup Trigger: Connect an existing "Join Now" button to a HulkApps/Custom Form. The form must open as a popup without refreshing the page.

OTP Verification: Implement Mobile Number OTP verification within the form before submission.

Auto-Location: Enable auto-detection of City/State based on the user's Pincode or IP.

Payment Redirect: Upon successful form submission, the user must be redirected to a specific Razorpay Payment Page URL.

API Automation (Pabbly/Webhook): Integrate the form with ShreeSMS (for SMS) and Mart2Meta (for WhatsApp) using APIs or Pabbly Connect.

Theme Compatibility: Ensure the code is clean and doesn't conflict with the Shopify Horizon theme's existing scripts.

Technical Stack:

Shopify Liquid, JavaScript (AJAX), CSS.

HulkApps Form Builder (or similar).

Pabbly Connect / Webhooks.

SMS/WhatsApp API Endpoints.