Shopify online Store

We have an existing AU store on OpenCart 3.0.2 and we’re launching a new NZ Shopify store on BBBBBB.co.nz using the Warehouse theme (~250 products). Shipping is from Australia to New Zealand.
Critical requirement: NZ must NOT be treated as a duplicate clone of AU. We need cross-domain hreflang (en-AU / en-NZ) across products + collections + key pages, with self-canonicals on both sites (never canonical NZ → AU) and NZ-only content blocks on every product page.
Domains
• AU (existing): https://www.AAAA.com.au (OpenCart 3.0.2)
• NZ (new): https://www.AAAAA.co.nz (Shopify)
Scope
1. Warehouse theme setup + electronics navigation (mega menu, shop by brand/use-case)
2. Migrate ~250 products (titles/descriptions/specs/images/SKUs) OpenCart → Shopify
3. Create collections to match AU categories
4. Add NZ localization blocks on all product pages + rewrite collection descriptions
5. Install/configure essential apps (Judge.me, Shopify Inbox, Chaty WhatsApp, Bulk editor, Search & Discovery, Bundles, reporting)
6. Payments: PayPal, Shopify Payments, bank transfer, Afterpay, Zip
7. International SEO: cross-domain hreflang + self-canonicals on both stores
Hreflang Implementation (must be automated, not manual forever)
• Create a mapping sheet (AU URL ↔ NZ URL + handles + SKUs)
• Shopify: metafields custom.au_url + output hreflang in theme.liquid
• OpenCart: mapping file/table keyed by SKU/category/page + inject hreflang in header/controller
Optional paid test: hreflang for 5 products + 2 collections end-to-end.
To apply
• Share 2–3 examples of cross-domain hreflang you implemented
• Confirm you can safely edit Shopify theme.liquid + OpenCart 3.0.2 header/controller
• Describe your mapping approach (Sheet → Shopify metafields → OpenCart mapping)
• Confirm: self-canonicals only (no NZ → AU canonical)