Personal tourist visa, can I cancel the hotel reservation and stay at a friend's house after the visa is issued?

Specific situation, specific analysis.

It depends on which country the visa is from.

There are different ways to deal with different situations.

Generally speaking, most popular tourist countries can do it.

Hotel reservation is only used for visa application. As long as you don't want to stay, you can cancel in advance.

Therefore, when booking a hotel, it is best to book a hotel that can be cancelled without a deposit.