Payment gateways like Paypal, Payoneer, Wise, etc
It is helps in reducing the chances of fraund, so advisable.
You can know about the prising structure here.
From next project onwards, have prising structure in place, invoice ready and don't start without advance payment
You can define your own pricing terms in the invoice
Eg: You can take 20% payment as advance, another 30% payment after the completion of 40% of your project.
No, never deposit any money to client to get a work, You can say no directly, Becoz there are 99.9% chances that it is fraud.
You can buy any advane course to upskill yourself and improve the quality of your services and thus increase your charges
Depends on which payment gateway you are using. Different payment gateway have different charges.
Aadhar card, Pan card, bank details
Its is unregulate, so not advisable to take payment in crypto
UPI is best, can also use razorpay
You can also stop the work