Explanation:

The principles of accounting are essential for maintaining the accuracy and reliability of financial records. The following are the principles of accounting that must be followed to ensure the accuracy of financial statements.

Accrual Principle:
The accrual principle is the accounting principle that requires revenue and expenses to be recognized in the period in which they are earned or incurred, regardless of when cash is exchanged. In other words, revenue is recognized when it is earned, and expenses are recognized when they are incurred.

Conservatism Principle:
The conservatism principle is the accounting principle that requires accountants to anticipate losses when there is uncertainty about the outcome of a transaction. Under this principle, losses are recognized immediately, but gains are recognized only when they are realized. This principle is used to ensure that financial statements are not overstated.

Consistency Principle:
The consistency principle is the accounting principle that requires a company to use the same accounting methods for similar transactions from one period to the next. This principle ensures that financial statements are comparable over time and that financial results are not distorted by changes in accounting methods.

Going Concern Principle:
The going concern principle is the accounting principle that assumes that a company will continue to operate indefinitely. This principle is used to ensure that financial statements accurately reflect the company's long-term financial position.

In the given scenario, Gyan received Rs.5,000 in advance, but he credited it to the sale account. This means that he recognized revenue even though it was not earned yet. This violates the accrual principle of accounting, which requires revenue to be recognized only when it is earned. Therefore, the concept that Gyan did not follow is the Accrual Principle.

Conclusion:
In conclusion, it is important to follow the principles of accounting to ensure the accuracy and reliability of financial statements. The principles of accounting are the Accrual Principle, Conservatism Principle, Consistency Principle, and Going Concern Principle.

Principle of conservatism states that one should consider the expected losses but not the expected revenues. But here Gyan considered his future revenue by crediting sales. so he is not following the principle if conservatism.