None. There are no such prerequisites to learn Salesforce but a little understanding of databases and any programming language is an advantage.
Whoever wants to learn Salesforce from scratch should go through these tutorials specifically profiles like Developers, System Administrators, IT Managers, Product Managers and Sales Representatives
We at S2 Labs have created a free Salesforce Administrator and Salesforce App Builder tutorial series which will not only help you learn it but will also be sufficient to crack the Salesforce Administrator and Salesforce App Builder certification.
These tutorials will include the notes, 70+ hours video lectures, 25+ hands-on assignments, 2 live projects and a test series which will help you get practical exposure and also crack the certification exam.
You need to create a webassessor account and then register for the exam using it. Here’s a it:
video that will help you with
Only 1. If you are not able to pass it then you will have to pay the retake fees which is USD 100 to appear for the exam again. (No one who studied from S2 Labs paid it yet 😉 )