Multiplatform Mobile App with Offline Sync Backend and Payment Gateway

Hello, I am looking for the best freelancer to develop a small android app to let users register the warranties of their personal equipments in an online database and able to warn the user when an equipment will soon be out of warranty. *** Please read the following App Specifications carefully and Quote accordingly only if you understand 100% please / Not personalized messages and copy/paste project descriptions will not be taken into account *** Platform : - Android Phones and tablets, iPhone and iPad, Windows Phone 10 Dev language and framework - Ideally Xamarin *Forms* and C Sharp - Syncfusion Framework or other platform like Cordova/JS Database - online (mbaas : Backendless, Azure, Kumulos or make proposal according to your experience) - ideally with offline sync Payment solution - recurring payments, Paypal, Stripe, other Functionalities - Register / Login - CRUD + list new equipments with : - description of equipment - serial Number - supplier's name - purchase date of equipment - camera pictures and other document upload functionality - end of warranty reminder profile - Setup - CRUD + list of reminders profiles (ex. warn me by email 1 month before end of warranty date and by sms 1 week before end of warranty date, etc) - print options - download options - ReadMe Text for contact and conditions - Functionality limitations according to user's profile : - Free : max 10 records / max 5 Mb for images and files per record / warning reminder max. 24 months - Standard : max 50 records / max 5 Mb for images and files per record / warning reminders max. 24 months - Pro : max 200 records / max 100 Mb for images and files per record / warning reminders max. 72 months - Recurring annual upfront payment - Automatic "End of warranty Soon warning message" through email, notification, sms, other. Project Deliverables : - Free / Standard / Pro Android, Iphone and WP apps - Fully documented source code - Stores ready - Backend Setup - Recurring payment solution in place - 1 year warranty on bugs Payment conditions : To be discussed, but min. 50% upon completion. Thanks.